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Reasons for High Safety of Silent Generator Set

May. 25, 2020

This article will share the reasons for high safety of silent diesel generator set by Starlight Power.

1. Loss of magnetic protection

The loss-of-magnetization protection is used as the loss-of-magnetism fault protection for the generator excitation current to drop abnormally or disappear completely. It is composed of the excitation low voltage Ufd (P), system low voltage, static stability impedance, TV disconnection and other criteria that the setting value automatically changes with the active power, and acts on signalling and demagnetization. The excitation low voltage Ufd (P) criterion and static stability impedance criterion are both related to the static stability boundary. It can detect whether the generator loses static stability due to demagnetization. The static stability impedance criterion acts at the static stability boundary after demagnetization.

2. Overexcitation protection

Overexcitation protection is the protection of the overhigh working magnetic density of iron core caused by low frequency or high voltage of reaction generator. The over-excitation protection is divided into high and low two-stage fixed value. The low fixed value sends a signal after a fixed delay of 5s and reduces the excitation voltage. The high fixed value is demagnetized by an inverse time action. The upper limit of inverse time delay is 5 seconds, and the lower limit is 200 seconds.

3. Stator grounding protection

Generator stator grounding protection is a generator stator single-phase grounding fault protection, which consists of fundamental zero-sequence voltage and third harmonic voltage.  Single-phase ground fault of stator winding from fundamental zero-sequence voltage protector to 95% area of tail is composed of zero-sequence voltage principle reflecting generator and acts on demagnetization at time t1 (3S); The third-harmonic voltage protector to 30% area of tail of stater winding single-phase ground fault is composed of generator neutral point and the third harmonic principle and operates on the signal at time t2 (5S). Both constitute 100% stator grounding protection.

silent diesel generator set

4. Stator turn protection

It is composed of longitudinal zero-sequence voltage and faults in the negative sequence direction criterion, and PT disconnection blocking measures are set to serve as the main protection of the internal turn-to-turn, phase-to-phase short circuit and stator winding open welding of the generator. The fault component negative sequence direction criterion is realized by detecting the negative sequence power flowing out of the generator to achieve the longitudinal zero sequence voltage criterion by detecting the longitudinal 3U0 output from the 3PT open delta winding whose neutral point is directly connected to the generator neutral point but not ground .

5. Out-of-step protection

Protection uses three-impedance elements, through the change of the impedance trajectory to detect the number of slippage and determine the location of the oscillation center. In case of short circuit fault, system oscillation, voltage circuit disconnection, etc., the protection does not malfunction. Protection generally operates on signals; when the oscillation center is inside the generator-transformer group, the protection stage I starts to send a trip command via t1 (0.5s), acting on de-excitation and demagnetization; when the oscillation center is outside the generator-transformer group, protection stage II starts to send signal via t2 (2s). The protection is equipped with a current blocking device to ensure that the current does not exceed the rated out-of-step breaking current of the circuit breaker when the circuit breaker is opened.

6. Low frequency accumulation protection

Low frequency cumulative protection reflects the cumulative impact of the system frequency reduction on the steam turbine. The protection is composed of sensitive frequency relays and counters, which are blocked by the auxiliary contact of the outlet circuit breaker (that is, the low frequency cumulative protection also exits when the generator is out of operation), the cumulative system frequency is lower than the fixed frequency of 47.5 Hz. When the cumulative time reaches the set value of 3000 seconds, the signal will be sent after a delay of 30 seconds. The device can be monitored in real time when running: display of fixed value, frequency and accumulated time.

7. Excitation circuit overload protection

Excitation circuit overload protection is used to protect the rotor excitation circuit from overcurrent or overload. It is connected in a three-phase type and consists of two parts: timing and inverse time. The operation current of the definite time limit is set according to the condition of reliable return under normal operation and large rated current. After the time limit t1 (5s), it acts on the signal and reduces the excitation current; The action of the inverse time limit is determined according to the overload capacity of the generator excitation winding, and the protection action is demagnetized. The upper limit of the inverse time limit is 10 seconds.

8. Rotor point ground protection

The generator rotor point ground protection is used to reflect the generator rotor circuit point ground fault. The protection adopts the ping-pong switching principle. The positive and negative grounding voltage of the rotor circuit are sampled in turn. By solving two different grounding circuit equations, the grounding resistance and grounding position of the rotor are calculated in real time. The protection acts on the signal after a delay of 2 seconds.

9. Symmetrical overload protection

The protection device is composed of two parts: definite time limit and inverse time limit. The definite time limit part acts on the signal after 5 seconds. The inverse time action is determined by the generator's ability to withstand the overload current, and the action is resolved. The protection device can reflect the heat accumulation process of the generator stator.

10. Negative sequence overload protection

The definite time action current is set according to the negative sequence current value allowed by the generator for a long time and the unbalanced current value of the negative sequence current filter under heavy load, and it acts on the signal after a time limit of 3 seconds. The inverse time action is determined by the generator's ability to withstand the negative sequence current, and the action is demagnetization.

silent generator set


Note: Starlight Power company manufactures good quality silent diesel generator, power range is from 25kva to 3125kva. The characteristics of our soundproof diesel generator are given as below:

1. Low noise, overall compact structure, little space occupation;

2. The box body is detachable structure, it is made of steel plate, and the surface is coated with high performance antirust paint; meanwhile, it is with noise reduction and rainproof function.

3. The inside of the boby adopts multilayer barrier impedance mismatch noise elimination structure and built in large impedance silencer.

4. The box body structure design is reasonable; a large capacity oil tank is arranged inside the body; at the same time, two inspection doors are arranged at the left and right side of the body in order to facilitate the genset troubleshooting.

5. At the same time, the observation window and the emergency stop button are set on the box body so as to observe the running state of the genset as well as stop the machine at the fastest speed in case of emergency so as to avoid damage to the genset.

Silent generator brands: Cummins, Perkins, Volvo, Deutz, Ricardo, Yuchai, SDEC, Weichai, WUXI POWER, Baudouin, etc.

Alternators can select Stamford, Leroy-Somer, Engga, Siemens, Shanghai KEPU, Marathon, and our own brand alternator – Starlight.

Controller we provide SmartGen, Deep Sea, ComAp, etc.

If you are interested in our silent generator set, please contact us for the best price.

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