Generally applicable rules for connecting HV limiters

Four rules, which can be applied generally to protection in VN networks, follow the above characteristics:

  1. The overvoltage limiters, and the device that is to be protected must be connected to a common earthing system. The galvanic interconnection between the earthing terminals of the limiters and the earthing of the protected device must be as short as possible.
  2. The total length of conductors a and b connecting the limiters to the protected device must be as short as possible.
  3. It is always recommended that conductor b should be as short as possible, or at least shorter than conductor a.
  4. Strip conductors are more suitable for connections than those with circular cross-sections, for with the same cross-section strip conductors have smaller inductance and pulse losses of overvoltages in them are smaller. The minimum size of a connecting conductor is 6 mm. The minimum width of a strip conductor is 12 mm.

Above all, the reason for installing overvoltage limiters is to prevent any possible damage. A seemingly considerable cost of such protections tends to be only a fraction of a percent of the acquisition value of the technology protected, and a negligible sum for possible damage caused by the breakdown, and/or the destruction of technological equipment. Unprotected electric distribution systems, computers, and data networks always pose a considerable risk to their users. 

Single-line diagram of protection with the marking of sections of conductor a and conductor b

Layout of the earthing network of limiters at the transformer

 Connection of limiters to transformer

 Connection of the limiter: (a) correct connection, (b) incorrect connection