PT secondary pass-through breakdown and fuse grounding issue

What is N600? Does PT secondary refer to the grounding of the neutral point arrester?

There are two ways to ground PT: 1. Direct grounding of the neutral point; 2. Direct grounding of phase B, with the neutral point then grounded through a breakdown fuse. In fact, in power plants, the station service PTs generally use the second grounding method mentioned above; grounding phase B is only provided for synchronization devices. Synchronization devices (including synchronization testing relays and synchronization meters) need to connect to the voltages from both PTs in order to compare the phase difference, and these two voltages must share a common point in order to enable an accurate comparison. Additionally, simple wiring is also a byproduct. Can’t phase A or phase C be grounded? In principle, it’s possible, but *by convention, phase B is grounded; why go to the trouble of changing this, only to cause unnecessary difficulties in installation, debugging, and maintenance? However, for PTs with a V-V connection (many PTs used for phase synchronization have a V-V connection), the middle phase must be grounded; otherwise, the protective effect against high-voltage breakdown would be too indirect, and the middle phase is usually phase B. Why is the neutral point grounded through a blowout fuse? With phase B grounded, for phases A and C, whether it is to prevent high-voltage breakdown or lightning protection, they are too far away from the ground wire; therefore, a breakdown fuse is installed at the neutral point to compensate for this. The secondary circuit of a voltage transformer shall have only one grounding point. If there are two or more grounding points, when a grounding fault occurs in the power system, the ground potential differences between these points are significant. Such potential differences are applied to the secondary or tertiary circuits of the voltage transformer, resulting in changes in the magnitude and phase of the voltages on those circuits. This, in turn, can cause impedance protection or direction protection to malfunction or fail to operate properly. The secondary circuits of several groups of voltage transformers connected via the control room neutral busbar (N600) shall be grounded at only one point to N600 within the control room. Otherwise, since all groups of voltage transformers have grounding points in their secondary circuits, multiple grounding points will inevitably occur. This causes the ground potential to be applied to the secondary circuits, resulting in incorrect operation of the protection devices.

Are you sure that’s how all power plants operate? Didn’t you copy this from somewhere? I suggest you take a look at the recently released power plant diagrams. . .

To see which power plant has released new images, it depends on which design institute was involved, what size the units are—all these factors vary

I have Zhongnan, North China, Shandong, and State Nuclear. . . There’s nothing like what you said; it starts at 2X350MW.