What are the characteristics of inter turn short circuit protection of diesel generator sets?

1) When the stator winding of the generator set is short-circuited between turns, there are positive-sequence, negative-sequence and zero-sequence components in the short-circuit current, and the currents of each sequence are equal, and the non-periodic component also appears at the initial moment of the short-circuit.

2) When the generator set is short-circuited between different phase turns, there will be a short-circuit current of circulation.

3) When the coil of the stator winding of the generator set is short-circuited between turns, due to the destruction of the electromotive force balance between the three relative neutral points of the generator set A, B and C, when the zero sequence component in the three-phase unbalanced electromotive force is reflected to the voltage transformer, the output end of the open triangle winding has 3UO, and the zero sequence current generated in the primary loop will form a circulation current in the line between the two midpoints of the parallel branch winding.

4) Due to the short circuit between the turns of one phase, the negative sequence component appears, it generates a reverse rotation magnetic field, so that the current of double frequency is induced in the rotor circuit, and the current in the rotor in turn induces other harmonic components in the stator, so that the stator and the rotor repeatedly affect each other, and a series of harmonic components are generated in the stator and rotor circuit. Moreover, since a part of the coils in a phase is shorted, it may cause the armature reaction to be asymmetrical at different polarities, and also produce harmonic components in the rotor circuit.

5) The direction of the negative sequence power during the inter-turn short circuit of one phase is opposite to that of the negative sequence power when the generator set is asymmetrically short-circuited by other internal and external asymmetrical shorts.

It is more accurate to use the method of measuring inductance, and it is more accurate than measuring DC resistance.

Short circuit of the first and second turns.

Answer]: AA item, "Code for the Design of Relay Protection and Automatic Devices for Electric Power Installations" (GB T 50062-2008) stipulates that 3 10kV lines are equipped with interphase short circuit protection devices, and the backup protection should be in the early spike remote backup mode.

Item B, "Code for the Design of Relay Protection and Automatic Devices for Electric Power Installations" (GB T 50062-2008) stipulates that 3 10kV lines are equipped with interphase short-circuit protection such as devices, and two-stage current protection can be installed for unilateral power supply lines, the first section should be a current quick break protection without a time limit, and the second section should be a current quick break protection with a time limit.

Item C, Article 1 of the Technical Regulations for Relay Protection and Safety Automatic Devices (GB T 14285-2006) stipulates that if the voltage of the bus used in the power plant or the bus of important users is less than 60% of the rated voltage and the cross-section of the line wire is too small, and it is not allowed to cut the fault with a time limit, the fault should be quickly removed.

Item D, Article 1 of the Code for the Design of Relay Protection and Automatic Devices for Electric Power Installations (GB T 50062-2008) stipulates that for double-sided power lines, current quick break and overcurrent protection with or without direction can be installed. When the current quick break and overcurrent protection with or without direction cannot meet the requirements of selectivity, sensitivity or quick action, the optical fiber longitudinal differential protection should be used as the main protection, and the current protection with or without direction should be installed as backup protection.

The characteristics of inter-turn short-circuit protection of diesel generator set, when the generator stator winding is short-circuited between turns, there are positive sequence, negative sequence and zero sequence weights in the short-circuit current, and the current of each sequence is the same, and the initial moment of short circuit also presents non-periodic weight. In addition, its characteristics are introduced as follows: 1. Because of the short circuit between the turns of a phase, the negative sequence weight is presented, and the magnetic field of reverse rotation occurs, so that the current of twice the frequency is induced in the rotor circuit, and the current in the rotor in turn induces other harmonic weights in the stator, so that the stator and the rotor repeatedly affect each other, and a series of harmonic weights occur in the stator and rotor circuit.

And because part of the coil in a phase is shorted, the armature response at different polarities can be asymmetrical, and harmonic weight will also occur in the rotor circuit.

2. The direction of the negative sequence power during the inter-turn short circuit of one phase is opposite to that of the negative sequence power when the generator is otherwise asymmetrically short-circuited internally and externally.

3. When the generator is short-circuited between different turns, it will inevitably present a short-circuit current of circulation.

4. When the coil of the generator stator winding is short-circuited between turns, because the electromotive force balance between the three relative neutral points of the generator A, B and C is destroyed, when the zero sequence weight in the three-phase unbalanced electromotive force is reflected to the voltage transformer, the output end of the open triangle winding has 3UO, and the zero sequence current in the primary circuit will form a circulation current in the line between the two midpoints of the parallel branch winding.

The composition of inter-turn protection of large generators usually has the following ways: 1. Horizontal difference protection: It is used when the stator winding has parallel branches and there are six lead-out heads on the neutral point side of the generator.

The cross-difference protection wiring is simple, the action is reliable, and the sensitivity is high. 2. Inter-turn protection based on the principle of zero sequence voltage: a special voltage transformer is used to measure the zero sequence voltage generated by the asymmetry of the three phases of the generator, which greatly improves the sensitivity and reliability of the protection due to the use of third harmonic braking.

3. Negative sequence power direction inter-turn protection: the use of negative sequence power direction to judge whether the generator internal asymmetry or system asymmetric fault, the sensitivity of the protection is very high, in recent years, the operation shows that the protection must increase the action delay when the fault occurs outside the area, so it restricts its use.

Hope it helps.

At present, the neutral point of large turbine generators has only 3 lead-out heads, and the horizontal difference cannot be realized. Moreover, the 6 million units of our power plant are not equipped with turn-to-turn protection, and it is not known if there are any million units equipped with this protection