GB 1094.2-2013Power transformers -- Part 2: Temperature rise for liquid-immersed transformers (English PDF)

4.1 Glyph

Cooled transformers shall be marked manner. For liquid-immersed transformers, the cooling mode using the following four letters mark.

The first letter (on behalf of the internal cooling medium).

--- O. mineral oil ignition point of not more than 300 °C or synthetic insulating liquid;

--- K. flash point greater than 300 °C of the insulating liquid;

--- L. ignition undetectable insulating liquid.

The second letter (on behalf of internal cooling medium circulation patterns).

--- N. liquid flow flowing through the cooling device and the winding interior natural convection circulation;

--- F. cooling liquid flow is forced circulation, the flow of liquid flowing through the windings inside the convection loop;

--- D. cooling liquid flow is forced circulation, and at least in the main flow of the liquid inside the winding guide is forced circulation.

The third letter (on behalf of external cooling medium).

--- A. air;

--- W. water.

The fourth letter (on behalf of external cooling medium circulation patterns).

--- N. natural convection;

--- F. forced circulation (fans, pumps, etc.).

Note 1. This section, K classes and use of L-based insulating fluid only from an environmental and safety point of view to consider.

Note 2. forced liquid circulation guide (second letter D) transformer flows through the main liquid flow is determined by the winding of the pump, in principle, by the negative Upload decision. Flowing through the cooling apparatus of a small portion of the liquid flow rate can be controllably directed flow through other parts of the core and the main winding outside, so that it cooled. Tap winding and/or other smaller capacity windings may be non-oriented liquid recycle.

In unguided forced liquid circulation (second letter F) transformer flows through the liquid flow is all windings with the load changes, and cooling equipment the pump flow is not directly related.

4.2 Transformer cooling with a variety of ways

A transformer may require several different cooling. In this case, the specification and the plate should be given under different cooling capacity Value, so that in the case of a cooling capacity required by and run when the transformer temperature does not exceed the limits, see GB 1094.1.

Capacity at maximum cooling capacity is the value of the transformer (transformer winding or a winding, see GB 1094.1) rated capacity, not with the cooling arrangement according to the cooling capacity is increased in the order.

For example.

--- ONAN/ONAF. transformer with a group of fans, when a large load, the fan can be put into operation. In either cooling mode, Liquid flow according to the thermal convection cycle;

--- ONAN/OFAF. transformer equipped with pumps and fan type cooling equipment, also provides natural cooling in (for example. Auxiliary Case of a power failure or lack of capacity) reduced capacity.

5.1 Air cooling transformer

Power Transformer normal ambient temperature limits see GB 1094.1.

Taking into account the requirements of normal temperature, the temperature of the transformer installation site should not exceed.

--- Any time. 40 °C;

--- Hottest average. 30 °C;

--- Average. 20 °C.

Note. Average temperature weather data obtained by the following (see GB 1094.1).

--- Monthly average temperature. a month, half of the average number of years of statistics the average daily maximum temperature and the daily minimum temperature and the;

--- The annual average temperature. throughout the year, and the monthly average temperature of 1/12.

5.2 Water cooling transformer

Normal cooling conditions for the water cooling of the transformer at the cooler inlet temperature of cooling water at any time should not exceed 25 °C or the annual average temperature should not exceed 20 °C.

If the water temperature exceeds the value of the runtime, provision should be low temperature (see GB 1094.1).

6.1 Overview

Temperature requirements shall be specified following different options.

--- At the rated capacity of a set of requirements for continuous operation (see 6.2);

--- If the specified duty cycle should be explicitly given a set of additional requirements relating thereto (see 6.4).

Note. This additional set of requirements is mainly used in the system of large transformers, because in an emergency under a load operation requires special attention. Generally should not use for medium and small transformers.

This section assumes that, each part transformer operating temperature of the external cooling medium (cooling or ambient air around the water) and the temperature of the portion and the temperature rise.

Except as otherwise specified, the normal temperature limits apply. There are other provisions, the temperature limit of 6.3 should be amended.

The temperature rise limit does not allow positive deviation.

Temperature limits rated capacity under 6.2 for tapping range does not exceed ± 5%, and the rated capacity of not more than 2500kVA (single-phase 833kVA) transformer temperature rise limits applicable for rated voltages corresponding to the main tap (see GB 1094.1).

For tapping range exceeding ± 5% or greater than the rated capacity 2500kVA transformer capacity in the appropriate tap, tap voltage and points Then current, temperature rise limits apply to all tap.

Note 1. The points took different load loss is different, and when the predetermined time-varying magnetic flux regulator, no-load loss is different.

Note 2. For independent winding transformer, its biggest loss of load tap generally has a maximum current tap.

Note 3. For tapped autotransformer, it has a maximum load loss depends on the tap tap arrangement.

For multi-winding transformer, when a rated capacity equal to the remaining winding rated capacity and its temperature requirement refers to all Windings are simultaneously in their respective rated load. If not the case, you should choose one or more of the specific load combinations, and accordingly the provisions of its temperature limits.

In part two or more windings of the transformer is arranged in the upper and lower case, if they are the same size and rating, the winding temperature rise Limits apply to the average of the measured values of the two windings.

Table 1 shows the temperature rise limits apply to have IEC 60085:2007 provided a solid insulation system temperature of 105 °C insulated and must

Edge of the liquid is a mineral oil or ignition of not more than 300 °C of synthetic liquid (the first letter of cooling is O) of the transformer.

These limits refer to continuous operation at rated capacity and external cooling medium annual average temperature value under steady-state conditions at 20 °C for.

If the user between producing and unless otherwise specified, the temperature rise limits given in Table 1 and modified for kraft paper (see also GB/T 1094.7) are be applicable.

Table 1 temperature rise limit

Claim

Temperature rise limit Top insulating liquid 60 the average winding (electricity group measurement).

--- ON and OF cooling

--- OD cooling

Winding hot spot 78

For the core, exposed electrical cables, electromagnetic shielding and structural parts on the tank, not a predetermined temperature limits, but still requires a temperature rise not Energy is too high, so as not to adjacent components subjected to thermal damage or excessive aging of the insulating liquid.

Note 4. Some of the design, in order to meet the winding hot spot temperature rise limit, may require an insulating liquid or top average winding temperature rise is less than a predetermined value in Table 1.

Note 5. the winding hot spot temperature rise of the method, see 7.10.

Note 6. For the oil dissolved gas analysis (DGA) was immersed in mineral oil in a large power transformer temperature rise test is carried out as a means to find abnormal overheating (See Appendix A).

Note 7. For large power transformers, fuel tank and fuel tank cap temperature rise can be used infrared cameras to check.

For a lot of resistance bolted particularly small winding (for example. some of the furnace transformer low-voltage winding), measured by the resistance method around the mean temperature rise may be very difficult, and the measurement uncertainty is large. In this case, after consultation with users of manufacturing, winding temperature rise can only claim in hot temperature, this hot temperature should be obtained by direct measurement.

For high-temperature flame-retardant insulation system or immersion liquid (the first letter of cooling is K or L) of the transformer temperature rise limits, Accordance with those agreements.

6.3 Special cooling requirements amended

6.3.1 Overview

If the intended installation site does not meet normal operating conditions, cooling conditions given in Chapter 5, the transformer temperature rise limit should be given below the rule amendments.

6.3.2 Air cooling transformer

If the temperature of the external cooling medium installation site has one or more of the normal value exceeds 5.1 is given, then all given in Table 1 the temperature rise limit value exceeded should be amended, and shall be rounded to the nearest integer value of temperature (K).

Table 2 Recommended ambient temperature reference value and the corresponding temperature limit correction value.

Table 2 under special operating conditions recommended temperature limits for correction value

Ambient temperature

Average monthly maximum Temperature rise limit correction value Ka 253545-5 304050-10 354555-15

Table 1 is a value relative.

Note 1. For ambient temperatures below Table 2 is not given provisions. If the user unless otherwise specified, in Table 1 temperature limits apply.

Note 2. The values listed in Table 2 can be obtained by interpolation.

If the installation site altitude above 1000m, while test site altitude less than 1000m, the test is allowable temperature rise limits the following provisions shall be reduced.

--- For the self-cooling (cooling mode after the two-letter symbol for AN) transformers, top liquid temperature, winding and winding average temperature rise Hot temperature limits should be part of the installation site is higher than the altitude of 1000m, 400m when reduced for each additional 1K;

--- For air-cooled (cooling after the two-letter symbol for AF) transformer shall be at the installation site altitude above 1000m Part of the time for each additional 250m decrease 1K.

If the test site altitude above 1000m, and the installation site altitude less than 1000m, the reverse should be amended accordingly.

Due to altitude and temperature do correction value shall be rounded to the nearest integer value temperature.

When the temperature is high due to the cooling medium or high altitude installation site and will reduce the transformer temperature rise limits specified shall mark on the nameplate (see GB 1094.1).

Note 3. When a standard transformer intended for use in high-altitude areas, reducing the value of its capaci...