2 The basics regulating P-coil
Neutral point treatment with P-coil one the most important ways improving the
voltage quality power grids. Although this was the obvious thing do, it
doesn’t always achieve the desired result today's grids.
The main advantage this technique the ability continue operating the network dur-
ing single pole-to-earth fault.
Overcompensation and undercompensation are only recommended for special applications
or overhead transmission grids with higher unbalance.
In the past, the only controlled variable that was used regulate coil was the absolute
value the zero sequence voltage UNE.
. This why other techniques have used
to regulate the coil.
6. The increase power lines has
balanced the grids and reduced the zero sequence voltage. (For more information, please see the chapter Current injection).2. This done setting the coil (in the grid's healthy
state) inductive resistance that corresponds approximately the grid's capacitive
resistance XC.
Medium voltage grids should compensated much possible that only the residual
current flows across the faulty section when earth fault occurs.1 Definitions
REG-DP/ REG-DPA Regulator for P-coil
EOR-D Earth fault detection relay
CI Current injection
CIC Current injection controller
ASC Arc suppression coil (Petersen coil, P-coil)
'UNE' Large index for primary quantities
'Une' Small index for secondary quantities
HPCI High-power current injection (for regulation and location detection)
6.Page 19
Applications
6. But the load can still affect the
zero sequence voltage and cause flicker.1 The basics resonant earthing
In medium and high voltage grids, Petersen coils are used compensate the capacitive
current across the faulty section similarly large counter-flowing inductive current when
a single phase-to-earth fault occurs
