ABB Relion 670 series, Technical Reference Manual

Page: 385 / 1232

Section 7 Current protection
About this chapter
This chapter describes current protection functions. These include functions like
Instantaneous phase overcurrent protection, Four step phase overcurrent protection,
Pole discrepancy protection and Residual overcurrent protection.
7.1 Instantaneous phase overcurrent protection 3-phase
output PHPIOC (50)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Instantaneous phase overcurrent
protection 3-phase output
PHPIOC
3I>>
SYMBOL-Z V1 EN
50
7.1.1 Introduction
The instantaneous three phase overcurrent function has a low transient overreach and
short tripping time to allow use as a high set short-circuit protection function.
7.1.2 Principle of operation
The sampled analog phase currents are pre-processed in a discrete Fourier filter (DFT)
block. The RMS value of each phase current is derived from the fundamental
frequency components, as well as sampled values of each phase current. These phase
current values are fed to the instantaneous phase overcurrent protection 3-phase output
function PHPIOC (50). In a comparator the RMS values are compared to the set
operation current value of the function
Pickup . If a phase current is larger than the set
operation current a signal from the comparator for this phase is set to true. This signal
will, without delay, activate the output signal TR_x(x=A, B or C) for this phase and the
TRIP signal that is common for all three phases.
1MRK505222-UUS C
Section 7
Current protection
379
Technical reference manual