ABB Relion 670 series, Technical Reference Manual, Page: 497 / 1232

Section 8 Voltage protection
About this chapter
This chapter describes voltage related protection functions. The way the functions
work, their setting parameters, function blocks, input and output signals and technical
data are included for each function.
8.1 Two step undervoltage protection UV2PTUV (27)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Two step undervoltage protection UV2PTUV
3U<
SYMBOL-R-2U-GREATER-THAN
V2 EN
27
8.1.1 Introduction
Undervoltages can occur in the power system during faults or abnormal conditions.
Two step undervoltage protection (UV2PTUV, 27) function can be used to open circuit
breakers to prepare for system restoration at power outages or as long-time delayed back-
up to primary protection.
UV2PTUV (27) has two voltage steps, each with inverse or definite time delay.
8.1.2 Principle of operation
Two-step undervoltage protection (UV2PTUV ,27) is used to detect low power system
voltage. UV2PTUV (27) has two voltage measuring steps with separate time delays. If
one, two or three phase voltages decrease below the set value, a corresponding
PICKUP signal is generated. UV2PTUV (27) can be set to PICKUP/TRIP based on
1
out of 3 , 2 out of 3 or 3 out of 3 of the measured voltages, being below the set point. If
the voltage remains below the set value for a time period corresponding to the chosen
time delay, the corresponding trip signal is issued. To avoid an unwanted trip due to
disconnection of the related high voltage equipment, a voltage controlled blocking of
the function is available, that is, if the voltage is lower than the set blocking level the
1MRK505222-UUS C
Section 8
Voltage protection
491
Technical reference manual