NB/T 10606-2021Code for Design of DC Auxiliary Power System for Hydropower Plants (English PDF)

Foreword

This document was issued on 26 April 2021 by the National Energy Administration of the PRC and takes effect on 26 October 2021.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 27.140, Chinese classification P59.

This code was approved and issued by the National Energy Administration through Announcement 2021 No. 3, together with other energy industry standards; it is listed as item 19 of Annex 1, approved on 2021-04-26 and implemented from 2021-10-26.

In accordance with the requirements of the Notice of the National Energy Administration on Issuing the Second Batch of Energy Sector Standard Formulation (Revision) Plans for 2013 (Guo Neng Ke Ji [2013] No. 526), the drafting group carried out extensive investigation and research, carefully summarized practical experience and, on the basis of widely soliciting opinions, formulated this code.

The main technical contents of this code are: general provisions, terms, basic requirements, system design, selection of battery, selection of battery charger, selection of DC cables, DC distribution equipment and cabinets, other equipment, and equipment arrangement and installation.

This code is under the administration of the National Energy Administration and is proposed and routinely managed by China Renewable Energy Engineering Institute; the Energy Industry Hydropower Electrical Design Standardization Technical Committee (NEA/TC17) is responsible for the explanation of specific technical contents. Comments and suggestions arising during implementation should be sent to China Renewable Energy Engineering Institute (Address: No. 2 Liupukang Beixiaojie, Xicheng District, Beijing; Postcode: 100120).

Chief development organization of this code: PowerChina Zhongnan Engineering Corporation Limited.

Chief drafting staff of this code: Luo Yun, Huang Kaibin, Li Li, Wu Xiang, Liu Chunqing, He Hexun, Deng Shuangxue, Zhang Qiang, Xu Lijia, Zhu Yijun, Cai Xu, Ye Xiaoli.

Chief reviewers of this code: Liu Guoyang, Yu Qinggui, Liu Shuyu, Wang Jinfu, Huang Huimin, Chen Jun, Chen Jiaheng, Feng Hanfu, Lin Jiemei, Wang Weifu, Zeng Gengyun, Song Guo, Gong Yu, Chen Qiang, Zhu Jiayong, Wang Bo, Xia Yongqiang, Huang Xiansheng, Xiong Jing, Du Gang.

1 Scope

NB/T 10606-2021 is the Chinese design code for the DC auxiliary power systems of hydropower stations, including pumped storage plants. The DC system is the part of a power station that must keep working when everything else has failed: it supplies the protection relays, the control and signalling circuits, the circuit breaker trip coils, the emergency lighting and the uninterruptible supplies, and it does so from batteries when the AC supply is lost. The code sets the general provisions and a full set of defined terms, then the design of the system: the choice of nominal voltage, the number of battery sets and chargers, and the connection schemes for the main plant, the switchyard, the dam and the auxiliary buildings. It covers the calculation of DC loads and their classification by duty, the determination of battery capacity by the step-by-step and the capacity conversion methods, and the selection of battery type. The charging and floating equipment follows, with its rating, ripple and regulation, then the DC distribution network with its protective devices, their selectivity and the cable sizing for voltage drop. Insulation monitoring and earth fault location, the monitoring and control of the system, and the arrangement of battery rooms and distribution panels with their ventilation and fire protection complete the code. It applies to the design of hydropower and pumped storage stations in China.

1.0.1 This code is formulated with a view to making the DC auxiliary power systems of hydropower plants safe and reliable, economical and rational, technically advanced, energy-saving and environmentally friendly, and convenient to operate and maintain.

1.0.2 This code is applicable to the design of DC auxiliary power systems of new, reconstructed and expanded hydropower plants, including pumped storage power plants.

This code is not applicable to the design of DC power systems dedicated to communication in hydropower plants.

1.0.3 This code specifies the basic principles, the equipment selection and calculation methods and the technical requirements for the main equipment in the design of DC auxiliary power systems of hydropower plants.

1.0.4 In addition to this code, the design of DC auxiliary power systems of hydropower plants shall also comply with the current relevant national standards.

2 Terms

2.0.1 DC auxiliary power system: a system providing DC electric energy in a hydropower plant, generally consisting of batteries, battery chargers, distribution devices, and monitoring and protection equipment.

2.0.2 Nominal voltage of DC auxiliary power system: the given value of voltage used to designate or identify the voltage of the DC auxiliary power system.

2.0.3 Integrated AC and DC power supply equipment: equipment combining the DC power system equipment with one or more of AC uninterruptible power supply (UPS) equipment, DC inverter power supply (INV) equipment and DC/DC converter devices, sharing the batteries and uniformly monitored, which supplies the DC loads, AC loads and communication DC loads of the power plant.

2.0.4 Valve-regulated lead-acid cell: a sealed lead-acid battery with a safety valve, which allows gas to escape through the safety valve when the internal gas pressure exceeds a predetermined value. Valve-regulated lead-acid batteries are generally divided into the absorbed (starved electrolyte) type and the gel type, and electrolyte cannot be added under normal conditions.

2.0.5 Battery set: an assembly of multiple batteries electrically connected together and used as a whole.

2.0.6 Floating charge: the battery is connected to a constant-voltage power source in a state close to its rated capacity; the constant-voltage source supplies the loads and at the same time provides supplementary charging to the battery.

2.0.7 Equalization charge: charging continued to bring all batteries in a battery set to the same state of charge, as well as supplementary charging after a deep discharge of the battery set.

2.0.8 Nominal voltage of battery: the voltage value used to designate or identify a single battery.

2.0.9 Final voltage of battery: the minimum discharge voltage that a single battery shall maintain at the end of discharge, as required by the consuming loads, within the specified discharge time.

2.0.10 Floating charge voltage of battery: the allowable operating range of individual cell voltage, specified by the manufacturer, for a battery in the floating charge state.

2.0.11 Equalization charge voltage of battery: the allowable operating range of individual cell voltage, specified by the manufacturer, for a battery in the equalization charge state.

2.0.12 Battery duty cycle: the discharge period of the battery and its load characteristics when the AC power supply is lost.

2.0.13 Capacity of battery: the electric charge delivered by a battery under specified discharge conditions, usually expressed in ampere-hours (Ah).

2.0.14 Rated capacity of battery: the battery capacity measured under specified discharge current, discharge time, final discharge voltage and temperature conditions. For lead-acid batteries the 10 h rate capacity (C10) is usually designated as the rated capacity.

2.0.15 Continuous load: a load supplied continuously by the DC power system both when the AC power supply is normal and when the AC power supply fails.

2.0.16 Noncontinuous load: DC loads other than continuous loads. During the battery duty cycle a noncontinuous load may last for the entire duty cycle, may be disconnected automatically or manually after lasting for a period, or may last only a very short time.

2.0.17 Momentary load: a relatively large noncontinuous load occurring within a short time, with a duration not exceeding 1 min.

2.0.18 Emergency load: a load that the DC power system shall reliably supply during an accidental outage of the AC power system.

2.0.19 Random load: a DC load in the battery duty cycle whose starting time cannot be predicted but which may occur at any time.

2.0.20 Power load: loads such as DC motors, UPS, inverter power supplies and emergency lighting.

2.0.21 Control load: loads such as control, signal, measurement, protection and automatic devices.

2.0.22 Load factor: a composite coefficient used in DC load statistics which comprehensively considers the ratio of actual power in normal operation to maximum power of the equipment, the ratio of actual current to maximum current, and the simultaneity factor of the various loads.

2.0.23 Disconnecting element: a disconnector, a combined electrical apparatus, or a circuit breaker meeting the isolation function, which provides isolation of the electrical circuit in the open state.

2.0.24 Protection element: a circuit breaker, fuse or combined electrical apparatus having an overcurrent protection function for the electrical circuit.

3 Basic Requirements

3.0.1 The design of the DC auxiliary power system shall meet the requirements of the "unattended" (few people on duty) operation mode.

3.0.2 The DC power system shall supply DC loads such as control and protection, as well as uninterruptible power supplies and unit excitation initiation (field flashing).

3.0.3 In hydropower plants, DC power loads should share a common DC power system with DC control loads.

3.0.4 The DC power system shall not be used as the standby power supply for power loads of fire-fighting equipment such as fire water pumps, smoke control fans and smoke exhaust fans.

3.0.5 Where the DC power system also serves as the standby power supply for centralized fire emergency lighting, it shall comply with the relevant provisions of the current national standards GB 51309 Technical Standard for Fire Emergency Lighting and Evacuate Indicating System and GB 17945 Fire Emergency Lighting and Evacuate Indicating System.