-Permissible value according to increased vibration of directional power relay’s contact or current relay - permissible values for selected relay.

-For directional power relay and directional resistance relay, phase displacement is 50%.

3.Output voltage ofa secondary winding of current transformer in case short-circuit happens in protected zone shall be not higher than permissible value of relay protection and automation.

- In principle, protecting circuit can incorrectly trip or non-operation, if current circuit is damaged, it is only allowed to connect measuring devices through suitable auxiliacuryrent transformers, provided that main current transformer meets the requirements mentioned in Article433 in case that secondary circuit of the auxiliary current transformer is open.

Article 435. Usage of Fuses

A fuse or a fuse wire can be used instead of circuit breakers, automatic circuit breaker and protective relays for reducing protection cost, if the following requirements are satisfied.

-The fuse which satisfy required parameters (voltage and nominal current, nominal breaking current, etc.) can be selected.

-Satisfying requirements of selectivity and sensitivity as same as protective relay.

-Not impeding operation of automatic equipment (autoreclosingdevise, automatic closing standby power source, etc.) under working conditions of electrical equipment.

-The fuse which satisfies the load characteristics stipulated in the article 84 can be selected.

Chapter 5-2-2 Protection of Generators

Article 436. Relay Components for Generators

As stipulated in Technical Regulation.

Article 437. Differential Relays

Regarding the basic operating point of differential relays, erticalthev differential protection is operated with tripping current not higher than 0.6 Idđ. (Idđ is nominal current of power generator). For the indirectly cooled windings power generator with capacity up toMW,30 it is allowed to be

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protected with tripping current equal to 1.3 - 1.4 Idđ. Tripping test of protective relay should be carried out in case that the operating value is higher than Idđ.

In addition, ti shall decide the setting value verticalof differential relay not to operate against unbalanced transient current. (e.g. transformer relay against inrush current of transformer)

A protective relay should basically be arranged in each 3-phase. For power generator with capacity up to 30MW, it is allowed to use 2-phase protective relay system in case that an earth fault protection is available in two points.

Article 438. Differential Relays and Instantaneous Current Relays

For power generator with higher capacity but without particular output of each phase at the medium voltage side of stator, it can use quick-break protection instead of vertical differential protection.

For independent power generator with voltage over1kV and capacity up to 1MW, it is allowed to use external short circuit protection as short-circuit protection for phases in stator winding (refer to Article 443). Protective relay shall trip breakto all circuit breakers of power generator and magnetic extinguishers.

Article 439. Grounding Protection stator of the generator

Regarding the protective relay for the one phase ground fault in stator winding of power generator with voltage over 1kV, if the fault current is 5A or over, current protective relay which operates the fault current or its high harmonic wave can be applied.If it is necessary, to use zero-sequence current transformer directly installed at terminals of generator.

To guard against the problemsingle-phase earth fault in the stator winding of the generator with voltage above 1kV, natural capacitive currents at earth fault exceeds the value large enough for overcurrent relays to operate at the time of earth fault (regardless of whether or not compensation), It

must set operating value for the relay according to this current. Necessary to use a-sequencezero current transformer located directly at the output of the generator. Also can be used voltage protection to detect overvoltage order not in het case of capacitive currents is not big enough to start the overcurrent relays.

compensation on capacitive current in power network of power generator), insulating tester on busbar will be used to trip for sending signals.

In case that the zero-sequence current transformer is installed on power generator to protect ainstg one phase ground fault, it is necessary to use two-pole ground fault relay and this relay is connected to the above mentioned current transformer.

In order to improve the reliability of protective relay when operating at highfault current, relay with saturated current transformer should be used. Protectionshall be carried out instantly and tripas mentioned in the article 437 or the article 438.

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Article 440. Protection of Short Circuits in Coils

As stipulated in Technical Regulation.

Article 441. Negative Sequence Current Relays

To protect power generator with capacity over 30MWfrom asymmetric external short circuit, and from overload of negative sequence current, it is necessary to install the negative sequence current relay which will trip at 2-level time (refer to the article 443).

For power generator with directly cooled winding, multi-level time protectionor time dependent protection. At that time, 2leveltime and time of dependent shall particularity be not higher than permissible overload negative sequence current particularity.

For power generator with indirectly cooled winding, it is necessary to use time dependent protective relay with tripping current not higher than permissible negative sequence current of this power generator within 2 minutes. Minimum time level of the protection shall be not higher than permissible

time while short circuit touches two phases of power generator’s terminals.

Negative sequence current protective relay shall be equipped with more sensitive component to trip for sending signals with time independent protection particularity. Tripping current of this component shall be not higher than permissible long-term negative sequence current for this power generator type.

Article 442. Under Voltage Relays attached to Overcurrent Relays

Regarding the basic operating point of overcurrent relay with voltage restraint, for power generators with capacity exceeding 30MW, tripping current of this protection shall be equal to from 1.3 to 1.5 Idd and starting voltage shall be equal to from 0.5 to 0.V6dd. (Idd andVdd are nominal current and voltage of power generator). For power generator with capacity from over 1MWto 30MW, starting current of

this protection and starting voltage of under voltage circuit will be taken according to the above mentioned values , starting voltage of relay for filtering sequence voltage is equal to from 0.1 to 0.2Vdd.

Article 443. Symmetric Overload Protection of Stators

For protecting power generator with voltage over1kV and capacity to MW1 from external short circuit, it is necessary to use over-current protective relay connected to current transformer installed at neutral terminal side of power generator. Selection of calibrated values shall be based on load current at necessary reserve. The low-voltage protection is also allowable (without current relay).

For protecting generators with capacity over 1MW from external short circuit the following requirements shall be satisfied:

-Protective relay shall be connected to current transformer installed at neutral terminal side of power generator.

-If busbar with generator voltage is sectionalized, protection shall be at 2-level time: the first level - short duration - tripping sectionalizing circuit breaker; the second levellong duration - tripping circuit breaker of power generator and magnetic extinguisher.

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Article 444. Overload Protection of Rotors

For directly cooled winding power generator, it is necessary to be equipped with rotor overload protection while it operates with main or auxiliary exciter. Protection will trip at time dependent or independent particularity and react to once voltage or current increases highly in rotor winding. Protector will trip to break power generator and magnetic extinguisher. At shorter time, it shall trip for reducing load of rotor.

Power generator’s symmetrical overload protection shall use one-phase current of stator for time- over-current protection with tripping for sending signals.

In order to reduce the load or when directly cooled winding power generator is shut down automatically in case that symmetric overload occurred,it is allowed to usethe above mentioned

protection of rotor and trip at overload of rotor which caused overload of power generator.

Article 445. Protection of Grounding Faults at Exciters

Protective relay for one-pole ground fault shall be equipped to detect such ground Thisfault. protective relay is used to detect one-pole ground fault, not tointerrupt exciter. It needs to equip one set of double-pole to ground fault (short circuit) protection in main exciting circuit of power generator. This protective relay shall be only put in operation in case that detection of one-pole to ground fault in exciting circuit during periodical check of insulation. Itshall interrupt circuit breaker and magnetic extinguisher of directly cooled winding generator and send the signals or interrupt power generator (in case of indirectly cooled winding power generator).

Article 446. Protection of Asynchronous and Loss of Field of Exciters

For power generator, it is necessary to install protective relay for asynchronous mode and loss of excitation. It is allowed to be superseded by automatic detector of asynchronous mode only by state of magnetic extinguisher. When protective relay trips or when automatic magnetic extinguisher (TDT) is interrupted, for power generator which is allowed to operate in asynchronous mode, it is necessary to trip for sending signal of loss of excitation.

Refer to Article 468 for power generators which are not allowed to operate in asynchronous mode.

Article 447. Overvoltage Protection for Generators

As stipulated in Technical Regulation.

Article 448. Circuit Breakers with Overcurrent Protection

In order to protect power generatorswith voltage up to 1kV and capacity up to 1MW with ungrounded neutral pole from all types of faults and abnormal operating modes, it is allowed to install automatic circuit-breakers with over-current interrupter, or circuit breakers with over-current protective device on 2-phase. In case that power generator has terminal at the neutral side, if possible, such protective devices should be connected to current transformer installed at this terminal.

For the above-mentioned power generators but with solidly groundedsystem, the protective devices on 3-phase shall be arranged.

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