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Transformer Cooler Operation Problem Discussion Area

Please God at the bottom of the article for these questions to discuss the message, welcome to actively discuss:

One, step-down low-voltage side of the single-phase ground protection action

This has been discussed in this case, no discussion here, only as a conclusion to summarize the relevant summary see annex.

Second, the pressure drop ground problem:

1, step-down Transformer Cooler core and clamp grounding and transformer shell grounding together; (whether to comply with specifications)

2, the core and the folder pieces of ground to share a lead wire grounding, and the core and clamp pieces were grounded through the lead wire separately ground way which is better?

Transformer Cooler core, clip pieces were led by a small casing shell, and then ground. Normal operation, the two cases are no different, when the main transformer inside the folder and the core of the ground or the core multi-point grounding, there will be different:

1), the main Transformer Cooler core and clamp pieces through the wire or high resistance after grounding, if the main transformer core and clamp pieces of ground to share a lead wire grounding, due to the main transformer running magnetic flux leakage, will be in the core - clip - The outer core and the clip piece loop form the circulation I, But this circulation does not flow through the outer lead into the earth. So there will be an external lead can not measure the ground current of large defects.

2), the main Transformer Cooler core and clamp through the wire or high resistance after grounding, if the main transformer core and clamp pieces are grounded through the lead wire separately, will be in the core - core grounding point - folder grounding - The loop is formed in the loop, which passes through the external lead, so it is easy to measure the increased ground current at the external ground lead monitoring and the A and B monitoring points are as large as the current.

3) the main Transformer Cooler occurs in the case of multi-point grounding, because the folder and the earth can not form a conductive circuit, so the A monitoring point can not monitor the current increase in the case, and the core in the core - ground lead - the earth - the other core of the core to form a loop, so the B monitoring point can be measured to a large ground current.

Therefore, the use of this grounding method, can further distinguish the main Transformer Cooler internal ground defects, as we judge the fault to provide a reliable basis.

3, the pressure Transformer Cooler shell no direct lead wire grounding, but through the base ground, whether in line with specifications. (# 3 step-down).

Step-down transformer shell grounding for the protection of the ground, when the Transformer Cooler insulation fault occurs, the shell close to the ground potential, to avoid personal shock. According to GB50148-2010 4.12.1 Article 5 requirements, the Transformer Cooler body should be two-point grounding (some information that can be grounded, is correct?). According to the requirements of the program, the transformer base and the base plate welding can not be regarded as effective grounding, only as a means of anti-operation when the Transformer Cooler shift. I stand # 3 step-down transformer shell grounding through the core and clip pieces share a grounding point grounding, not through the reserved grounding point for grounding, whether in line with technical specifications? Whether it should be reserved at the grounding point of the transformer body, with grounded flat iron and the main grounding network for direct grounding. (The following figure shows the grounding point of my station # 3 main transformer, with the core and clip pieces share a ground, and the shell only this one grounding point, the other grounding points are ground)