GB/Z 34935-2017Technical specifications for oil-immersed smart power transformers (English PDF)

Foreword

This guiding technical document was drafted in accordance with the rules given in GB/T 1.1-2009.

This guiding technical document was proposed by the China Electrical Equipment Industry Association.

This guiding technical document is under the jurisdiction of the National Technical Committee on Transformers of Standardization Administration of China (SAC/TC 44).

Drafting organizations of this guiding technical document: China Electric Power Research Institute, Shenyang Transformer Research Institute Co., Ltd., Shandong Electrical Equipment Co., Ltd., Beijing Sifang Automation Co., Ltd., Shanghai Ruikai Electric Co., Ltd., XD Xi'an Transformer Co., Ltd., Baoding Tianwei Baobian Electric Co., Ltd., TBEA Hengyang Transformer Co., Ltd. and Dalian Shiyou Electric Power Technology Co., Ltd.

Main drafters of this guiding technical document: Gao Fei, Zhang Xianzhong, Li Bo, Zhang Zhongguo, Liu Youwei, Zhao Xiaoyu, Li Jinzhong, Wang Xingang, Huang Xin, Wang Fu, Zhi Ying'an, Cheng Congming, Zhang Yongxin, Deng Yanguo, Xiao Yan, Tang Hao, Zhang Shuqi, Jia Pengfei, Yu Xinru and Wang Shiyou.

1 Scope

This guiding technical document specifies the terms and definitions, general rules, configuration, and testing, commissioning and acceptance of oil-immersed smart power transformers.

This guiding technical document applies to the design, manufacture, inspection and selection of oil-immersed smart power transformers (hereinafter referred to as 'smart transformers') for systems with a nominal voltage of 66 kV to 750 kV.

The design, manufacture, inspection and selection of other smart transformers may be carried out with reference to this guiding technical document.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 1094.1 Power transformers - Part 1: General; GB/T 1094.2 Power transformers - Part 2: Temperature rise for liquid-immersed transformers; GB/T 1094.3 Power transformers - Part 3: Insulation levels, dielectric tests and external clearances in air; GB/T 1094.4 Power transformers - Part 4: Guide to the lightning impulse and switching impulse testing - Power transformers and reactors; GB/T 1094.7 Power transformers - Part 7: Loading guide for oil-immersed power transformers; GB/T 1094.10 Power transformers - Part 10: Determination of sound levels.

GB/T 2423.1 Environmental testing for electric and electronic products - Part 2: Test methods - Test A: Cold; GB/T 2423.2 Environmental testing for electric and electronic products - Part 2: Test methods - Test B: Dry heat; GB/T 2423.4 Environmental testing for electric and electronic products - Part 2: Test methods - Test Db: Damp heat, cyclic (12 h + 12 h cycle); GB/T 2900.95 Electrotechnical terminology - Transformers, voltage regulators and reactors; GB/T 4109 Insulated bushings for alternating voltages above 1 000 V; GB/T 6451 Specification and technical requirements for oil-immersed power transformers; GB/T 7252 Guide to the analysis and the diagnosis of gases dissolved in transformer oil; GB/T 7354 Partial discharge measurements.

GB/T 17626.2-2006 Electromagnetic compatibility - Testing and measurement techniques - Electrostatic discharge immunity test; GB/T 17626.3-2006 Radiated, radio-frequency, electromagnetic field immunity test; GB/T 17626.4-2008 Electrical fast transient/burst immunity test; GB/T 17626.5-2008 Surge immunity test; GB/T 17626.6-2008 Immunity to conducted disturbances induced by radio-frequency fields; GB/T 17626.8-2006 Power frequency magnetic field immunity test; GB/T 17626.9-2011 Pulse magnetic field immunity test; GB/T 17626.10-1998 Damped oscillatory magnetic field immunity test.

GB/T 30155 Technical guide for smart substations; DL/T 860 (all parts) Communication networks and systems in substations; DL/T 1411 Technical guide for smart high-voltage equipment; JB/T 10088 Sound levels of power transformers from 6 kV to 1 000 kV.

3 Terms and definitions

For the purposes of this document, the terms and definitions given in GB/T 1094.1 and GB/T 2900.95 and the following apply.

3.1 smart power transformer: a transformer composed of an oil-immersed power transformer body (hereinafter 'transformer'), sensors built into or mounted outside the transformer body, and an intelligent component, which realizes functions such as intelligent operation, condition monitoring and control of the transformer or its components. 3.2 sensor: a device or apparatus that converts specific condition information into electrical information that can be acquired. 3.3 intelligent component: an assembly integrating several intelligent electronic devices, having all or part of the functions of transformer condition signal acquisition, condition monitoring, operation control, fault identification and non-electrical protection.

3.4 intelligent electronic device (IED): a device with a processor having all or part of the following functions: acquiring or processing data; receiving or sending data; receiving or sending control commands; executing control commands. 3.4.1 monitoring IED: part of the intelligent component that acquires transformer condition information to assess its operating state and/or control state and/or loading capability. 3.4.2 controlling IED: part of the intelligent component used for networked and/or intelligent control of the transformer or its components, usually also monitoring the controlled components. 3.4.3 main IED: part of the intelligent component that aggregates the information of the IEDs in the intelligent component and assesses operation reliability, control reliability and loading capability of the transformer, to support grid operation control and/or condition-based maintenance. 3.4.4 non electric protection IED: part of the intelligent component used for non-electrical protection of the transformer.

3.5 merging unit (MU): a device that merges and synchronizes the electrical quantities transmitted from primary instrument transformers and forwards the processed digital signals in a specific format to bay-level equipment. 3.6 operation reliability: the probability that, under normal operating conditions, the continuous operating time t reaches or exceeds a given duration T (T > 0), expressed as P{t >= T}; where not specified, T = 1 week may be used. 3.7 control reliability: the probability of responding to a control command and achieving all operating objectives under permitted working conditions. 3.8 loading capability: the maximum load a transformer can bear for a given continuous operating duration, or the maximum duration it can operate continuously under a given load; generally determined by the hot-spot temperature limit of the transformer.

3.9 monitoring data: data or data sets reflecting the operating state of the transformer, acquired by monitoring IEDs or other IEDs with monitoring functions. 3.10 formatted data: monitoring data sets generated by monitoring IEDs and controlling IEDs with monitoring functions from monitoring data files according to the data completeness requirements of the production management information system. 3.11 concluded information: in-depth processing of monitoring data into concise information on operation reliability, control reliability and loading capability, provided to the dispatching (control) centre.

3.12 fingerprint current: characteristic information of a current signal, such as amplitude, time and waveform, usually compared with the initial current signal under identical or similar working conditions to detect equipment defects. 3.13 server: a functional node in a communication network that provides data to other functional nodes or allows them to access its resources; it may also be a logical sub-part of a software algorithm (and/or hardware) structure whose operation is independently controlled. 3.14 warning: a parameter value deviates from the normal state and should attract attention. 3.15 alarm: a parameter value reaches a state endangering equipment safety and shall be dealt with immediately or as soon as possible.

4 General

4.1 Composition of the smart power transformer. A smart power transformer consists of the transformer body, sensors built into or mounted outside the transformer body, and the intelligent component. The intelligent component is connected to the sensors and/or actuators by cables, optical fibres, etc. A schematic diagram of the typical composition is given in Figure A.1, and the recommended typical intelligent component in Figure A.2.

4.2 Basic functions. The basic smart functions (see the relevant provisions of GB/T 30155) are: a) condition monitoring of the transformer through sensors and the intelligent component; b) evaluation of monitoring data to form concluded information, reported via the substation communication network to the monitoring host and the dispatching (control) centre, supporting safe operation of the grid; c) processing of monitoring information to form formatted data, reported via the substation communication network to the integrated application server and the production management information system, supporting condition-based maintenance; d) intelligent control of the controlled components.

4.3 Main characteristics. 4.3.1 Digitized measurement: basic condition information of the transformer, such as switch positions and warning/alarm information, is measured digitally on site. 4.3.2 Networked control: the transformer or its components are controlled over a remote communication network, including receiving and responding to control commands and feeding back control status. 4.3.3 Functional integration, in three aspects: a) sensor installation shall be included in the design of the transformer body or its components; b) the information flow of the intelligent component and its IEDs shall be designed in a unified way; c) the integrated design shall meet sensor installation requirements while ensuring safe operation of the transformer.

4.3.4 Interactive information: the IEDs within the intelligent component, and the intelligent component and other equipment, shall be able to exchange information as needed to support the smart functions of 4.2. In accordance with GB/T 30155, concluded information and formatted data are reported by the main IED to station-level equipment (see Figure A.2); information supporting real-time control should be connected to security zone I, otherwise to security zone II. For monitoring IEDs without a main IED, formatted data may be reported directly to the integrated application server. 4.3.5 Condition information sharing: equipment condition is presented to the dispatching (control) and maintenance centres in the form of concluded information.

4.4 Basic technical requirements. 4.4.1 Transformer body: a) it shall meet existing transformer technical specifications; b) it shall meet 4.3.3, and the insulation level, sealing performance and mechanical strength of the body shall not be affected, nor shall operation reliability, control reliability or economic life be reduced.

4.4.2 Sensors and installation: shall comply with item a) of 4.3.3 and: a) sensors shall meet relevant standards and requirements; b) installation and failure shall have no adverse effect on transformer operation; c) they shall be compatible with the transformer body; d) they shall withstand the electromagnetic, temperature, humidity, vibration and other environment at the installation location; e) they should be installed at earth potential; f) where earthing current sampling is needed, through-type (feed-through) current sensors should be used, ensuring the earthing lead has continuous and consistent current-carrying capacity; g) current sampling from control and drive circuits shall use through-type current sensors.

4.4.3 Intelligent component principles: a) each IED shall have clear functions to facilitate interchangeability and interoperability; b) monitoring IEDs may be configured separately per monitoring item or integrated; c) IED communication shall follow DL/T 860 (all parts); d) each IED shall support the characteristics of 4.3.1, 4.3.2, 4.3.4 and 4.3.5 and realize the functions of items b), c) and d) of 4.2 (see Figure A.2); e) IEDs may be installed in a dedicated intelligent component cabinet or arranged together with other secondary equipment of the substation according to engineering design; where a cabinet is used, its power supply and internal environment shall meet the operating requirements of the IEDs.

5 Configuration

5.1 Configuration principles of the intelligent component. A three-phase smart transformer should be provided with one set of intelligent component; a three-phase bank formed of single-phase smart transformers should also be provided with one set. The intelligent component should be placed in a cabinet or share cabinet (compartment, room) space with other secondary equipment.

5.2 Configuration of IEDs. The IED configuration is given in Table 1; the controlling IEDs may be independent devices or their basic functions may be realized by the main IED. Table 1 (smart items and IED configuration): basic state acquisition and non-electrical protection - merging unit, shall be used (5.3), and non-electrical protection IED, shall be used (5.4); control - cooling equipment control IED, shall be used except for natural cooling (5.5), and on-load tap-changer control IED, shall be used except for off-circuit tap changing (5.6); monitoring - dissolved gas in oil monitoring IED (5.7.2) and core and clamp earthing current monitoring IED (5.7.3), should be used for 220 kV/180 MVA and above; partial discharge monitoring IED (5.7.4), winding hot-spot temperature monitoring IED (5.7.5) and capacitive bushing monitoring IED (5.7.6), optional (the hot-spot temperature IED is only suitable for newly manufactured transformers); aggregation and analysis of monitoring information - main IED, shall be used (5.8).

5.3 Merging unit. The merging unit acquires the analogue signals output by the bushing current transformers of the transformer body and combines them with time. Configuration: a) for transformers of 220 kV to 750 kV system nominal voltage, 2 sets per group of instrument transformers should be provided; b) for 66 kV to 110 kV, 1 set per group; c) for main transformers with duplicated protection, 2 sets per group.

5.4 Non-electrical protection IED. The non-electrical protection IED and the body intelligent terminal may be realized in one device, with interfaces for DC quantity acquisition, tap-changing blocking, starting forced-air cooling and starting nitrogen-injection fire extinguishing; the non-electrical protection IED should integrate the body intelligent terminal function. It shall: a) use the oil-flow protection contacts of the body gas (Buchholz) relay and of the on-load tap-changer for non-electrical protection tripping, other contact signals being handled per relevant standards (Table 2); b) for single-phase transformers, input the A, B and C non-electrical protection signals per phase, with the three phases sharing one function pressing plate for tripping; c) connect to the substation network, reporting non-electrical warning or alarm information to the bay control device or monitoring system and protection operation information to the bay control device, monitoring system and dynamic recorder.

Table 2 (non-electrical protection IED configuration): basic state quantities - body gas (light gas), body oil level, body oil temperature 1 and 2, winding temperature 1 and 2, tap-changer oil level, tap-changer oil temperature 1 and 2 (tap-changer items optional when no independent OLTC control IED is provided); non-electrical protection information - body oil-flow surge (heavy gas) 1 and 2, body pressure, total cooler shutdown, tap-changer oil-flow surge (heavy gas), tap-changer pressure; protection tripping output - trip command and operation information. Notes: the two heavy-gas contacts of a double-contact Buchholz relay should be combined with AND logic, with an alarm when a single contact operates alone (maloperation); total cooler shutdown shall act as instantaneous or definite-time output depending on transformer temperature.

5.5 Cooling equipment control IED. 5.5.1 It shall receive or acquire control-related information (Table 3); cooling is generally controlled by top-oil temperature and load current; where fibre-optic temperature measurement exists, the control strategy shall give priority to winding temperature control while considering energy-saving operation, control the cooling equipment, receive its feedback and report alarms such as total cooling shutdown via the substation network. 5.5.2 It may also monitor the cooling equipment operating state (parameters in Table 3) and shall form 'operation reliability' concluded information of the cooling equipment. 5.5.3 It is generally under autonomous control.

Table 3 (cooling equipment control IED): control basis - transformer top-oil temperature (shall be selected), bottom-oil temperature and winding hot-spot temperature (shall be selected if available), each 0 °C to 150 °C with 2 °C uncertainty (other ranges may be chosen by the user); load current (shall); ambient temperature (should). Alarm information - fan overcurrent trip, oil pump overcurrent trip, oil-flow relay operation signal, abnormal total cooling shutdown (shall); power supply normal/abnormal (should). Monitoring information - cooler inlet and outlet oil temperature (optional, 0 °C to 150 °C, 2 °C); operating state (shall); oil pump current, fan current and supply voltage (optional, range covering the dynamic operating range, 2.5 %); formatted data and concluded information (shall, when monitoring information exists). Control command - group control (mandatory).

5.6 On-load tap-changer control IED. 5.6.1 The OLTC IED shall receive and respond via the substation network to the control commands of Table 4 and feed back control status; 'constant voltage' is a control mode in which the OLTC IED autonomously keeps the voltage within a range; where master-slave (synchronous) control is required, the OLTC IED shall support it. 5.6.2 To ensure safe OLTC operation, the OLTC IED should have the intelligent blocking functions of Table 4 and report blocking information to the bay control device; high oil viscosity blocking is based on the OLTC tank oil temperature. 5.6.3 The OLTC IED shall have alarm functions (Table 4) reported via the substation network; with master-slave control, parallel operation abnormality alarms shall be included (multiple masters, no master, multiple control of slaves, inconsistent tap positions, master-slave communication interruption). 5.6.4 It may monitor OLTC condition and should autonomously assess operation reliability and control reliability, forming corresponding concluded information.

Table 4 (OLTC control IED): control commands - raise one step, lower one step, emergency stop (shall), go to specified position (should), constant voltage (optional). Intelligent blocking - overvoltage, undervoltage and low oil temperature blocking (optional), overcurrent blocking (shall). Control feedback - current tap position, highest position reached, lowest position reached, local/remote operation (shall). Monitoring information - OLTC tank oil top temperature (optional; shall when low oil temperature blocking is configured) -5 °C to 150 °C, 2 °C; OLTC tank oil level 0 % to 100 %, 5 %; voltage and current of the winding concerned (shall when over/undervoltage or overcurrent blocking is configured); drive motor supply voltage Vd, 2.5 %; drive motor current Ad, 2.5 %; drive motor current fingerprint: normal, slight change, significant change; total number of operations 0 to 100 000, uncertainty 0; contact wear 0 % to 100 %; formatted data and concluded information (shall, when monitoring information exists). Alarm information - incomplete OLTC changeover/operation not completed, operation blocking alarm, drive motor overcurrent blocking (shall); oil top temperature abnormal contact, high and low oil level contacts (should); online oil filter trip signal (shall, when a filter is fitted); drive motor supply abnormal contact (optional); parallel operation abnormality (should, with master-slave control).

5.7 Monitoring IED. 5.7.1 General requirements: monitoring IEDs shall be selected according to actual engineering needs. Formatted data and concluded information shall be reported to the main IED via the substation network; the reporting period may be 2 h, with one additional report if a monitored quantity changes by more than 5 % since the last report. Each monitoring IED shall have sufficient storage and a suitable storage strategy for trend and in-depth analysis.

5.7.2 Dissolved gas in oil monitoring IED: monitors all gases of interest (H2, CH4, C2H4, C2H2, C2H6, CO) or only key gases such as H2 and C2H2, and may be extended to CO2 and H2O; it shall meet Table 5 and form formatted data 'H2, CH4, C2H2, C2H4, C2H6, CO, CO2, H2O' and 'operation reliability' concluded information, with null values for absent quantities. Table 5 (minimum detectable value; range; uncertainty, whichever is greater): H2 5 µL/L, 5-2 000 µL/L, 5 µL/L or 30 %; C2H2 0.5 µL/L, 0.5-100 µL/L, 0.5 µL/L or 30 %; CH4 1 µL/L, 1-1 000 µL/L, 1 µL/L or 30 %; C2H4 0.5 µL/L, 0.5-1 000 µL/L, 0.5 µL/L or 30 %; C2H6 0.5 µL/L, 0.5-1 000 µL/L, 0.5 µL/L or 30 %; CO 25 µL/L, 25-5 000 µL/L, 25 µL/L or 30 %; CO2 50 µL/L, 50-15 000 µL/L, 50 µL/L or 30 %; H2O (moisture) 0 mg/kg, 0-100 mg/kg, 2 mg/kg or 10 %. The minimum detectable value may be adjusted by weighing other trade-offs; uncertainty requirements may be relaxed appropriately in service.

5.7.3 Core and clamp earthing current monitoring IED: monitors the earthing current of the core and clamps to detect multi-point earthing faults promptly. Measuring range 1 mA to 10 A, uncertainty 1 mA or 3 % (whichever is greater). It shall form 'measured current value' formatted data and 'operation reliability' concluded information. 5.7.4 Partial discharge monitoring IED: monitors internal discharge signals of a certain intensity and tracks their development; values may be expressed in pC or dB, and sampled values of the relevant merging unit should be received via the substation network as analysis reference. Based on monitoring data of 50 consecutive power-frequency cycles it shall form 'discharge magnitude, discharge frequency (number of times exceeding the attention level)' formatted data and 'operation reliability' concluded information.

5.7.5 Winding hot-spot temperature monitoring IED: usually fibre-optic sensors measure the winding hot-spot temperature directly; the number of measuring points (usually 4 to 20) is agreed between user and manufacturer, and their locations are determined by internal temperature field calculation or measurement (see GB/T 1094.2). Measuring range shall cover -40 °C to 200 °C, uncertainty not greater than 2 °C; merging unit sampled values shall be received as analysis reference. It shall form formatted data 'temperature of point 1, point 2 ... point n, ambient temperature, load factor (present load/rated load)' and concluded information 'hot-spot temperature, permissible continuous operating time (see GB/T 1094.7)', with null values for absent quantities. 5.7.6 Capacitive bushing monitoring IED: monitors bushing capacitance, generally only for capacitive bushings of 220 kV and above, uncertainty not greater than 1 %; the dielectric dissipation factor may also be monitored with uncertainty not greater than 0.001. It shall form 'capacitance change rate %, dielectric dissipation factor, ambient temperature' formatted data and 'operation reliability' concluded information.

5.8 Main IED. The main IED receives via the substation network the concluded information and formatted data of all monitoring IEDs, the relevant merging unit sampled values and the monitoring information of controlling IEDs, and by comprehensive analysis forms concluded information 'operation reliability (overall), control reliability (OLTC), permissible duration at the present load level', sending it and the formatted data to the relevant equipment as required by items b) and c) of 4.2. It may also have the auxiliary function of continuously acquiring basic state quantities such as core earthing current, oil level and oil pressure. Table 6 (main configuration): monitoring IED reported information - concluded information (shall have; receives messages of monitoring IEDs) and formatted data (shall have; receives and forwards messages); integrated information - concluded information (shall have; sends messages). Table 7 (auxiliary configuration, optional, analogue acquisition): core earthing current 1 mA to 10 A, 3 %; conservator oil level 0 % to 100 %, 5 % (absolute); conservator oil pressure in MPa (range covering dynamic operating range), 5 %.

6 Testing, commissioning and acceptance

6.1 Tests of the intelligent component. The following tests shall be performed, a) and b) being type tests and c), d) and e) routine tests: a) conformance and interoperability testing of each IED according to DL/T 860 (all parts); b) environmental and immunity tests - where conditions permit, the intelligent component should be tested together with its cabinet as a whole, otherwise each IED separately (test levels may be adjusted for the in-cabinet environment); environmental tests per GB/T 2423.1, GB/T 2423.2 and GB/T 2423.4, and immunity tests per GB/T 17626.2, 17626.3, 17626.4, 17626.5, 17626.6, 17626.8, 17626.9 and 17626.10, checking all IED functions and performance item by item.

Required immunity levels (Clause 5 of each standard): 1) electrostatic discharge, GB/T 17626.2-2006, level 4; 2) radiated RF electromagnetic field, GB/T 17626.3-2006, level 3; 3) electrical fast transient/burst, GB/T 17626.4-2008, level 4; 4) surge, GB/T 17626.5-2008, level 4; 5) conducted disturbances induced by RF fields, GB/T 17626.6-2008, level 3; 6) power-frequency magnetic field, GB/T 17626.8-2006, level 5; 7) pulse magnetic field, GB/T 17626.9-2011, level 5; 8) damped oscillatory magnetic field, GB/T 17626.10-1998, level 5. c) Check that the permitted operating environment of each IED is consistent with the environmental control targets of the compartment or room housing the intelligent component; d) functional and performance tests at room temperature; e) continuous energization test. Test methods follow relevant standards.

6.2 Joint commissioning of the transformer body and the intelligent component. 6.2.1 General: for a newly manufactured smart transformer, type tests and relevant special tests of the transformer body shall be performed after the sensors and intelligent component are installed, together with joint commissioning of the smart functions. All sensors and components shall be in their actual working state; the intelligent control cabinet shall be no farther from the transformer body than in the actual site layout, including within the reference emitting surface; a separate power supply and earthing shall be used; the intelligent component shall be in normal operation; tests follow GB/T 1094.1, GB/T 1094.2, GB/T 1094.3, GB/T 1094.4, GB/T 1094.10 and GB/T 6451. Joint commissioning should be done together with the type tests or as agreed between user and manufacturer; its purpose is to verify the reliability and correctness of the intelligent component functions in the environment of routine, type and special tests. All measuring equipment shall be calibrated and within validity. Test items are 6.2.2 to 6.2.13.

6.2.2 Short-circuit impedance and load loss measurement (GB/T 1094.1, GB/T 6451): record transformer voltage and current measured by the IED; all sensors and components shall work normally without damage, and the difference between the RMS voltage and current measured by the IED and by calibrated laboratory equipment shall not exceed ±2 % of the IED full scale/laboratory measurement (example B.1). 6.2.3 On-load tap-changer test (GB/T 1094.1): record tap positions displayed by the OLTC control IED; they shall equal the actual positions, and raise/lower operations shall be performed continuously without error through the IED (example B.2). 6.2.4 Long-duration no-load test (GB/T 1094.1, GB/T 6451): record core earthing current IED results during the test and DGA IED results after; all components shall operate normally without damage, core earthing current shall not exceed 100 mA, and the DGA IED results shall follow the same trend as laboratory offline DGA with differences meeting Table 5 (example B.3).

6.2.5 Sound level determination (GB/T 1094.10, JB/T 10088): record the relative position of the intelligent control cabinet and the transformer body; criterion JB/T 10088. 6.2.6 Induced voltage test with partial discharge measurement (GB/T 1094.3, GB/T 7354): record PD measured by the PD monitoring IED, whose trend shall match that of calibrated laboratory equipment (example B.4). 6.2.7 Dissolved gas analysis of insulating oil (GB/T 7252): record DGA IED results before and after the dielectric tests, after the temperature-rise test and after the long-duration no-load test; trends shall match laboratory DGA with differences meeting Table 5 (example B.3.2). 6.2.8 Switching impulse test and 6.2.9 Lightning impulse test (GB/T 1094.3, GB/T 1094.4): no special data recording; all sensors and components shall show no damage, freezing or restart, and measured data and waveforms shall be normal (examples B.5, B.6).

6.2.10 Temperature-rise test (GB/T 1094.2): record the operation of the cooling control IED and top-oil temperature values or curves, and, with a fibre-optic winding temperature IED, hot-spot temperature values or curves. The cooling control IED shall start and stop fans according to top-oil temperature consistently with the control strategy; the top-oil temperature measured by the IED shall not differ by more than ±2 °C from calibrated laboratory equipment in the same thermometer pocket; fibre-optic hot-spot data and trends shall be reasonable. If the steady-state hot-spot temperature rise is lower than the average winding or top-oil temperature rise, fibre failure is suspected; if it exceeds the hot-spot limit, it shall be verified whether the fibre has failed or the hot-spot temperature rise is excessive. Note: measurement uncertainty should be considered (example B.7).

6.2.11 Pressure sealing test (GB/T 1094.1): openings made for sensor installation (sensors, oil sampling pipes, fibre feed-through plates, PD mounting flanges, etc.) shall not leak oil or deform, and original seals of the body shall not seep (example B.8). 6.2.12 Bushing capacitance and dielectric dissipation factor (tan delta) measurement (GB/T 4109): record values measured by the capacitive bushing IED; at the same temperature, frequency and voltage there shall be no obvious difference from calibrated laboratory equipment, the absolute error of tan delta shall not exceed ±0.001 and the relative error of capacitance ±2 % (example B.9).

6.2.13 Communication function test (DL/T 1411): during joint commissioning each controlling IED shall receive all control commands from the simulated station-level system, successfully operate the controlled components and correctly feed back control status; the non-electrical protection IED is tested manually for correct output signals and information flow; each monitoring IED and controlling IED with monitoring functions shall acquire at least one complete data set and complete one full information exchange, with monitoring parameters meeting DL/T 1411 (example B.10). 6.3 Acceptance: the manufacturer shall submit type test reports, routine test reports, joint commissioning reports, etc., all meeting the contract requirements.

Annex A (informative) Schematic diagrams of the smart power transformer

The typical composition of a smart power transformer is shown in Figure A.1 and the typical intelligent component in Figure A.2.

Figure A.1 shows the transformer tank with bushing current transformers (CT), temperature sensors (T), a PD sensor, gas relay (GR), DGA and H2O sensors, fibre-optic temperature sensors (OT) on the windings, the core earthing current sensor (I), the cooler (C) and the OLTC, wired to the OLTC control IED, cooling control IED, main IED, PD monitoring IED, DGA monitoring IED, winding temperature monitoring IED, non-electrical protection IED and HV bushing monitoring IED; these and the merging unit connect to the process-level network, and the main IED and control IEDs to the station-level network.

Figure A.2 shows the power transformer (OLTC actuators and sensors, cooler actuators and sensors, sensors, non-electrical quantities) connected to the IEDs of the intelligent component, with the main IED and bay control device linked to the station-level network (security zone I/II). Note 1: the main IED aggregates IED monitoring information to realize items b) and c) of 4.2 and may connect to zone I or II as required by dispatching. Note 2: controlling IEDs realize networked and/or intelligent control; switchgear controllers, OLTC control IED and cooling control IED may also monitor controlled components. Note 3: monitoring IEDs monitor HV equipment condition. Note 4: (1) protection relay trip command; (2) to the relevant protection relays; (3) trip command to switchgear controllers on each side. Note 5: the bay control device may be integrated into the intelligent component; if electronic instrument transformer sensors are integrated in the HV equipment, the merging unit should be integrated into the intelligent component.

Annex B (informative) Examples of test data records of the smart part in joint commissioning

B.1 Short-circuit impedance and load loss measurement. Table B.1 is a record form for the high-medium winding pair at HV tap positions 1, 9A and 17, with applied current and IED-measured current (A), measured voltage and IED-measured voltage (kV). Figure B.1 shows IED screenshots of HV three-phase values under high-medium loading: tap 1 about 547.4-548.2 A and 36.1-36.8 kV; tap 9 about 601.5-602.1 A and 31.3-32.2 kV; tap 17 about 668.1-669.2 A and 26.6-27.8 kV. Conclusion: no damage to sensors and components, data and waveforms normal, IED voltage and current measurements accurate and valid; test passed.

B.2 On-load tap-changer test. Table B.2 (OLTC IED performance test, with IED model and manufacturer) lists: 1) control commands, zero error required - raise one step, lower one step, emergency stop (switching quantities), local command control, and station-level command via the bay control device for remote tap changing, each requiring correct operation; 2) status return, zero error required - current position as switching quantity (one contact per position) and as analogue (BCD code), consistent with local position; highest position, lowest position, mechanism refusal/overcurrent blocking, OLTC supply breaker open, tap change in progress, local/remote operation and operation not completed, each requiring correct remote signalling. Figure B.2 shows station-level screenshots before, during and after raising the tap from position 10 to 11. Conclusion: all operations passed, OLTC control IED functions normal and position display correct.

B.3 Long-duration no-load test. B.3.1 All components shall operate normally without damage, with normal data and waveforms; core earthing current measured by the IED shall not exceed 100 mA; DGA IED results are recorded after the test. B.3.2 Table B.3 compares conventional instruments and the DGA IED before and after dielectric tests, after temperature rise and after long no-load for H2, CO, CO2, CH4, C2H6, C2H4, C2H2 and total hydrocarbons (µL/L) by gas chromatography, plus water content (mg/kg), tan delta (%, 90 °C) and breakdown voltage (kV). Figure B.3 shows DGA IED trend curves (methane, acetylene, total hydrocarbons, hydrogen, moisture, CO, CO2) over about 22 h, all below about 13 units. B.3.3 Figure B.4 shows the core earthing current reading (0.0250) and alarm indicator during the long no-load test. Conclusion: core earthing current and dissolved gas measurements correct; test passed.

B.4 Induced voltage test with PD measurement. B.4.1 The test voltage indication shall show no sudden drop, the continuous PD level at test voltage shall not exceed the required value nor show a continuously rising trend; the PD IED is calibrated with a standard source, sensitivity and trends at each voltage stage are recorded, and IED and laboratory PD trends shall match. B.4.2 Table B.4 records laboratory PD (pC, terminals A, Am, a) at 1.1Um/sqrt3 for 5 min, U2 = 1.5Um/sqrt3 for 5 min, U1 = 1.7Um/sqrt3 for 30 s, U2 = 1.5Um/sqrt3 at 5-minute intervals up to 60 min, and 1.1Um/sqrt3 for 5 min; HV tap position 5, frequency 200 Hz. B.4.3 Table B.5 (PD IED performance): UHF method with internal sensor and UHF signal output, range 300 pC to 10 000 pC (channels 1 and 2); minimum detectable discharge not greater than 300 pC; maximum not less than 10 000 pC; a chart shows the PD record of three channels from 11:00 to about 18:00.

B.5 Switching impulse test. B.5.1 and B.5.3: voltage and current oscillograms at full and reduced voltage are compared; if waveforms are not distorted and no sensor or component suffers damage, freezing or restart, with normal data and waveforms, the test is passed. B.5.2 Table B.6 (terminal A): 50 %-70 % switching wave -672.5 kV, T1 127 µs, Td 388 µs, T0 1 320 µs (No. 1); 100 % switching wave -1 162 kV, T1 128 µs, Td 410 µs, T0 1 420 µs (No. 2); oscillograms of voltage and current are shown (peak currents 39.11 A and 71.84 A).

B.6 Lightning impulse test. B.6.1 and B.6.3: full-wave and chopped-wave oscillograms at full and reduced voltage are compared with the same pass criterion. B.6.2 Table B.7 (terminal A): 50 % full wave 483.79 kV, T1 1.371 µs, T2 46.56 µs; 100 % full wave 950.73 kV, T1 1.406 µs, T2 47.06 µs; 50 % chopped wave 557.21 kV, T1 1.38 µs, Tc 2.89 µs, Oz 0.19; 100 % chopped wave 1 040.90 kV, T1 1.42 µs, Tc 2.34 µs, Oz 0.21; voltage and current oscillograms No. 1 to No. 4 are shown.

B.7 Temperature-rise test. B.7.1 Figure B.5 shows top-oil and average oil temperature rise curves over 9 h: top-oil rise peaks at about 49 K at 3.5 h and stabilizes near 43 K; average oil rise peaks at about 36 K and stabilizes near 31 K. B.7.2 Figure B.6 shows the IED top-oil temperature record rising from about 27 °C to about 43 °C. Figures B.7 to B.11 show oil-surface and fibre-optic IED data and trends during ONAF and ONAN stages: oil surface up to about 84 °C, HV phase A, B and C winding hot spots up to about 97-98 °C, and core up to about 85 °C. B.7.3 Figure B.12 shows cooling control IED screenshots before fan start, after starting the first fan group and after starting the second group.

B.8 Pressure sealing test. Table B.8: static oil column method, 30 kPa applied for 24 h, result no leakage or damage. Conclusion: openings for sensors, sampling pipes, fibre feed-through plates and PD flanges showed no leakage or deformation and original body seals did not seep; test passed. B.9 Bushing capacitance and tan delta measurement: Table B.9 records nameplate voltage (kV), manufacturer and serial number, and tan delta (%) and Cx (pF) measured conventionally and by the IED, both at 10 kV.

B.10 IED monitoring system tests (Tables B.10 to B.15). Table B.10 (non-electrical protection IED): body gas relay (light gas alarm, heavy gas trip), pressure relief valve (trip), dial oil-surface thermometer (alarm and trip at set temperatures), dial winding thermometer (hot-spot alarm and trip), OLTC gas relay (light gas alarm, heavy gas trip), body oil level gauge and OLTC oil level gauge (alarm above or below setting), OLTC pressure relief valve (trip); method for each: change remote signal state 10 times, all correct. Table B.11 (merging unit): acquisition of electronic current transformer signals within specified error; communication with measuring IEDs meeting SV processing requirements. Table B.12 (monitoring main IED, bay level) and Table B.13 (bay control unit): communication with sub-IEDs and with the back-end monitoring system per DL/T 860 (all parts). Table B.14 (back-end monitoring system, station level): communication with the main IED and bay control unit per DL/T 860. Table B.15: status check form for all IEDs after no-load, load, impulse, applied withstand voltage, short-duration and long-duration induced, long no-load and temperature-rise tests.