Protection of converter units

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 4. Switchgears and substations

Converter substations and installations. Protection of converter units

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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4.3.13. The transformer of the converter unit, depending on the typical power and primary voltage, must be equipped with the following protection devices:

1. Instantaneous overcurrent protection against multi-phase short circuits in the windings and at the transformer terminals and, if possible, against a short circuit in the converter, acting to trip.

The protection must be tuned in response current from magnetization current surges when an unloaded transformer is turned on and from possible load current surges; protection, as a rule, should be selective with respect to circuit breakers on the rectified voltage side and to fuses of semiconductor converters.

The protection operation must be ensured at all provided values of the secondary voltage of the transformer for the possible values of the transformation ratio.

In installations with a primary voltage above 1 kV, the overcurrent protection, as a rule, must be two-phase in a three-relay design.

In installations with a primary voltage of up to 1 kV, the transformer should be protected by an automatic switch having maximum current releases in two phases with an isolated neutral and in three phases with a solidly grounded neutral of the primary voltage network.

2. Gas protection against internal damage and low oil level in the transformer.

Gas protection should be installed on transformers with a capacity of 1 MB·A or more, and for intra-workshop converter substations and installations - on transformers with a capacity of 0,4 MB·A and more. The gas protection must act on the signal in case of weak gas formation and a decrease in the oil level, and on shutdown in case of intensive gas formation.

Depending on the availability of personnel or the timing of their arrival after the appearance of the signal, as well as on the design of the gas relay, protection may be provided to turn off when the oil level drops further. To protect against low oil level, a separate level switch can be used in the transformer expander.

3. Protection against pressure increase (pressure switch) of sealed transformers with its effect on the signal for transformers with a power of up to 0,63 MB A and with a shutdown action for transformers with a power of more than 0,63 MB A

4. Overvoltage protection on the secondary voltage side of the transformer with a rectified voltage of 600 V or more.

5. Breakthrough fuse installed in the neutral or phase on the low voltage side of the transformer, with a secondary voltage of up to 1 kV.

Tripping protective devices must act on the circuit breaker installed on the primary voltage side of the transformer and, if necessary, on the circuit breaker on the rectified current side of the converter unit.

4.3.14. The semiconductor converter, depending on the power, the value of the rectified voltage, type, purpose and mode of operation, in addition to the protection according to 4.3.13, must be equipped with:

1. Fast-acting fuses in each parallel branch to protect individual or series-connected valves. If two or more fuses blow, the converter unit must be automatically switched off. An alarm should be provided that responds to blown fuses.

2. A high-speed non-polarized automatic switch in one pole on the side of the rectified voltage for protection against interpole short circuits behind the converter and for protection against overturning of the inverter in reversible converter units when operating according to the block-converter-consumer scheme.

The number of circuit breakers required to protect the converter is also determined by the power circuit diagram of the converter and the consumer.

3. Protection for removing control pulses or shifting control pulses in the direction of increasing the regulation angle of thyristor converters to prevent overcurrents.

4. A high-speed non-polarized automatic switch in one pole during the operation of one or parallel operation of several semiconductor converters on a common busbar.

5. Protection against internal and external surges.

4.3.15. The converter unit must be equipped with protection, control and signaling devices that operate during the following abnormal operating modes:

1. Exceeding the permissible temperature of the oil or non-flammable liquid of the transformer.

2. Exceeding the permissible temperature of the water cooling the semiconductor converter.

3. Blown fuse in the power circuit of the semiconductor valve.

4. Termination of air or water cooling.

5. Long-term overload of the converter unit.

6. Lack of control pulses.

7. Damage (decrease in level) of the installation insulation.

8. Violation of work in other auxiliary devices of the converting unit, preventing its normal operation.

4.3.16. At converting substations (installations) with personnel on duty or when their operation is controlled by the dispatcher, the protection, control and signaling devices specified in 4.3.15, clauses 1-5, 7 and 8 must act on the signal, and those specified in 4.3.15, item 6, - to turn off the converter unit.

At converting substations (installations) without personnel on duty and without transmitting signals to the control room, the protection, control and signaling devices listed in 4.3.15 should act to turn off the converting unit.

In some cases, based on local conditions, the action of the devices specified in 4.3.15, paragraph 1, on the signal is allowed.

See other articles Section Rules for the installation of electrical installations (PUE).

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