Multi-generator ship intermediate voltage electric power system protection method and device

Abstract

The invention relates to a multi-generator ship intermediate voltage electric power system protection method and device. The method comprises the steps that a busbar of a ship intermediate voltage electric power system is connected with a grounding transformer which is connected with a resonance grounding device, each generator neutral point in the ship intermediate voltage electric power system is connected with a high-resistance grounding device, and the resistance value of the high-resistance grounding device is determined according to a multi-tapping mode. The high-resistance grounding device and the resonance grounding device are connected in parallel, so that protection is effectively provided for an intermediate voltage generator and the electric power system, and meanwhile the mixed grounding mode can be effectively used in the complex working conditions such as multi-generator parallel separation.

Description

technical field [0001] The invention relates to the technical field of medium-voltage power system protection for ships, in particular to a protection method and device for a medium-voltage power system of a multi-generator ship. Background technique [0002] In the ship power grid, the proportion of single-phase ground faults is greater than 50%, and more than 90% of single-phase ground faults will generate arcs. The arc overvoltage generated by single-phase grounding will affect the insulation of non-faulty phase cables to ground, and single-phase grounding faults can easily deteriorate into phase-to-phase faults, thus affecting the reliability and continuity of power supply of the system. [0003] The hazard degree and treatment method of single-phase ground fault are closely related to the grounding mode of the neutral point of the power grid. The high-resistance grounding method requires that the high-resistance grounding device can operate with a fault for 2 hours (hi...

AI Technical Summary

Problems solved by technology

Low-resistance grounding can effectively suppress overvoltage, but the current at the fault point is too large (up to 400A), which is easy to damage the equipment, and the damage to the generator in the low-resistance grounding method is calculated. Even if the generator trips immediately after a ground fault occurs, The fault energy is 67.2kJ, which is greater than the standard of 30kJ determined by Conrad, which means that the low-resistance grounding method has the problem of permanent burning of the stator core

For the resonant grounding method, in order to protect the generator, each generator needs to be connected to a resonant grounding device at the neutral point. When the generator needs to be disconnected from the grid quickly when a single-phase ground fault occurs, the setting of the resonant grounding device is delayed, which cannot be satisfied at this time. Generator Protection Requirements

At the same time, when several generators are running in parallel, the grounding devices need to communicate with each other, and a complex parameter setting method is required. This kind of grounding device is expensive and complicated, and has low reliability.

[0004] Most existing ships are powered by a single or two medium-voltage generators, but for applications that require power from multiple medium-voltage generators, the working conditions of the power system are complex, and multiple generators will frequently be disconnected in parallel according to changes in working conditions Due to the short distance between the cable and the steel plate of the hull, the load is large, and the capacitance of the system to the ground is large, the excessively large distributed capacitance will cause the zero-sequence current to rise when a ground fault occurs. Using the existing high-resistance grounding method, when a ground fault occurs The zero-sequence current is not allowed to exceed 10A, so the high-resistance grounding device cannot be applied under the condition of large system distributed capacitance

At the same time, the high-resistance grounding device must be connected to the neutral point of the generator. When multiple generators are connected in parallel, the equivalent grounding resistance value will drop, which will also cause the current at the fault point to rise. Therefore, the existing high-resistance grounding device with fixed resistance Does not provide good protection for multiple generators

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