Online monitoring and fault diagnosis technology for high-voltage switchgear

Online monitoring and fault diagnosis technology for high-voltage switchgear

High voltage switchgear can be divided into indoor and outdoor types. For 10kV and below, the user indoor type is commonly used. According to different primary line schemes, it can be divided into inlet and outlet switchgear, interconnection switchgear, bus section switchgear, etc. Most 10kV incoming and outgoing switchgear cabinets are equipped with low oil circuit breakers or vacuum circuit breakers. The circuit breakers are equipped with multiple spring or electromagnetic operating mechanisms, as well as manual or permanent magnet operating mechanisms. There are significant differences in the structure of different switchgear cabinets, which will affect the installation and selection of sensors.

1. Fault manifestations and causes of high-voltage switchgear

According to survey statistics, the faults of high-voltage switchgear mainly include the following categories:

(1) Refusal to operate or malfunction: This type of fault is the main fault of high-voltage switchgear, and its causes can be divided into two categories: one is caused by mechanical faults in the operating mechanism and transmission system; Another type is caused by electrical control and auxiliary circuits.

(2) Breaking and closing faults: These types of faults are caused by the circuit breaker body, and for low oil circuit breakers, they mainly manifest as fuel injection short circuit, arc extinguishing chamber burning loss, insufficient breaking capacity, and explosion during closing. For vacuum circuit breakers, it is manifested as air leakage in the arc extinguishing chamber and bellows, reduced vacuum, reignition of the capacitor bank, and ceramic tube rupture.

(3) Insulation fault: manifested as external insulation to ground flashover breakdown, internal insulation to ground flashover breakdown, interphase insulation flashover breakdown, lightning overvoltage flashover breakdown, porcelain bottle casing, capacitor casing flashover, pollution flashover, breakdown, explosion, lifting rod flashover, CT flashover, breakdown, explosion, porcelain bottle fracture, etc.

(4) Current carrying fault: The main cause of current carrying fault at voltage levels of 7.2~12kV is poor contact of the isolation plug in the switchgear, which leads to contact melting.

(5) External forces and other faults: including foreign object impact, natural disasters, small animal short circuits, etc.

2. The monitoring and diagnosis methods for high-voltage switchgear have different fault detection methods for different types of high-voltage switchgear:

(1) The online monitoring of mechanical characteristics includes: closing and opening coil circuit, closing and opening coil current and voltage, circuit breaker moving contact travel, circuit breaker contact speed, closing spring status, mechanical vibration during circuit breaker operation, statistics of circuit breaker operation times, etc.

At present, the mechanical status monitoring of circuit breakers mainly includes monitoring of stroke and speed, as well as monitoring of vibration signals during operation. The monitoring of mechanical vibration signals during circuit breaker operation is based on the changes in the occurrence time and peak value of each vibration signal, combined with the current waveform of the opening and closing coils, to determine the mechanical status of the circuit breaker.

A circuit breaker with stable mechanical performance has relatively stable peak values and time differences between the opening and closing vibration waveforms. The basis for determining whether the vibration signal has changed is to conduct multiple opening and closing tests on a new or overhauled circuit breaker, record a stable vibration waveform as the characteristic waveform "fingerprint" of the circuit breaker, and compare the vibration waveform measured in the future with the "fingerprint" to determine whether the mechanical characteristics of the circuit breaker are normal.

(2) Online monitoring of electrical performance includes monitoring of the weighted value of circuit breaker breaking current and the vacuum degree of the arc extinguishing chamber. Using the equivalent wear curves under different breaking currents, accumulate the relative electrical wear corresponding to each current breaking. The total allowable electrical wear of each circuit breaker is calibrated by its rated short-circuit breaking current and the number of times it is allowed to break the full capacity. The cumulative wear of the contact is used as the basis for determining its electrical life. Reference [5] elaborates on the factors that affect the contact life of vacuum circuit breakers and certain SF6 circuit breakers, and proposes an improved online monitoring method for the electrical life of vacuum circuit breakers. This method considers the actual breaking process and arcing time of each phase, greatly improving accuracy, and can more accurately reflect the electrical wear and tear situation of each phase.

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Datasheet
1.1 710-512-01-MVS1 Main Substation
Incoming Switchgear A01 B01 2
No Components Specification Unit Qty Maker
1 VCB
HVX12-50-31-F 275mm
Altitude ≤2000m
Opening voltage DC220V
Closing voltage DC220V
Energy storage voltage DC220V
Set 1 China
2 VT JDZ-10 10KV/√3/0.1KV/√3 Set 3 China
3 CT
LZZBJ9-12 3000/1A 5P20 10VA
5P20 5VA 5Fs5 5VA
Set 3 China
4 High voltage fuse XRNP1-12 0.5A Pc 3 China
5 Lightning arrester HY5WZ-17/50 Set 3 China
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7 Short circuit and ground fault indicator EKL-4-1 Pc 1 China
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10 Charged display DXN-12Q Pc 1 China
11 Temperature and humidity controller WY-CS-III Pc 1 China
12 Connecting piece JY-2 Pc 3 China
13 Junction box PJ1 Pc 1 China
14 Metering bracket Universal type Pc 1 China
15 Signal lamp ND16-22D/4 AC380V red Pc 1 CHNT
16 Signal lamp ND16-22D/4 AC380V green Pc 1 CHNT
17 Signal lamp ND16-22D/4 AC380V white Pc 1 CHNT
18 AC miniature circuit breaker NB1-63/2P C6A 6kA(R) Pc 2 Fengyuan
19 AC miniature circuit breaker NB1-63/3P C3A 6kA(R) Pc 1 Fengyuan
20 DC miniature circuit breaker NB1Z-63 2P C6 Pc 1 Fengyuan
21 AC miniature circuit breaker NB1-63/3P B2A 6kA(R) Pc 1 China
22 Universal test terminal RURTK/S Pc 30 China
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