selective tripping of a faulty line. Alternatively, the
function can be used solely for signaling of the earth-
fault location to the SCADA system when the power
network is allowed to operate for a longer time with an
earth-fault being present.
8. Voltage protection
Two-step undervoltage protection UV2PTUV
M13789-3 v13
Undervoltages can occur in the power system during
faults or abnormal conditions. The two-step
undervoltage protection function (UV2PTUV) can be
used to open circuit breakers to prepare for system
restoration at power outages or as a long-time delayed
back-up to the primary protection.
UV2PTUV has two voltage steps, each with inverse or
definite time delay.
It has a high reset ratio to allow settings close to the
system service voltage.
Two step overvoltage protection OV2PTOV
M13798-3 v17
Overvoltages may occur in the power system during
abnormal conditions such as sudden power loss, tap
changer regulating failures, and open line ends on long
lines.
Two step overvoltage protection (OV2PTOV) function
can be used to detect open line ends, normally then
combined with a directional reactive over-power
function to supervise the system voltage. When
triggered, the function will cause an alarm, switch in
reactors, or switch out capacitor banks.
OV2PTOV has two voltage steps, each of them with
inverse or definite time delayed.
OV2PTOV has a high reset ratio to allow settings close
to system service voltage.
Residual overvoltage protection, two steps
ROV2PTOV
M13808-3 v12
Residual voltages may occur in the power system during
earth faults.
Two step residual overvoltage protection (ROV2PTOV)
function calculates the residual voltage from the three-
phase voltage input transformers or measures it from a
single voltage input transformer fed from an open delta
or neutral point voltage transformer.
ROV2PTOV has two voltage steps, each with inverse or
definite time delay.
A reset delay ensures operation for intermittent earth
faults.
Overexcitation protection OEXPVPH
M13319-3 v9
When the laminated core of a power transformer or
generator is subjected to a magnetic flux density
beyond its design limits, stray flux will flow into non-
laminated components that are not designed to carry
flux. This will cause eddy currents to flow. These eddy
currents can cause excessive heating and severe
damage to insulation and adjacent parts in a relatively
short time. The function has settable inverse operating
curves and independent alarm stages.
Voltage differential protection VDCPTOV
SEMOD153862-5 v7
A voltage differential monitoring function is available. It
compares the voltages from two three phase sets of
voltage transformers and has one sensitive alarm step
and one trip step.
Loss of voltage check LOVPTUV
SEMOD171457-5 v8
Loss of voltage check (LOVPTUV ) is suitable for use in
networks with an automatic system restoration
function. LOVPTUV issues a three-pole trip command to
the circuit breaker, if all three phase voltages fall below
the set value for a time longer than the set time and the
circuit breaker remains closed.
The operation of LOVPTUV is supervised by the fuse
failure supervision FUFSPVC.
Radial feeder protection PAPGAPC
GUID-82856D0B-5C5E-499A-9A62-CC511E4F047A v3
The radial feeder protection (PAPGAPC) function is used
to provide protection of radial feeders having passive
loads or weak end in-feed sources. It is possible to
achieve fast tripping using communication system with
remote end or delayed tripping not requiring
communication or upon communication system failure.
For fast tripping, scheme communication is required.
Delayed tripping does not require scheme
communication.
The PAPGAPC function performs phase selection using
measured voltages. Each phase voltage is compared to
the opposite phase-phase voltage. A phase is deemed to
have a fault if its phase voltage drops below a settable
percentage of the opposite phase-phase voltage. The
phase - phase voltages include memory. This memory
function has a settable time constant.
The voltage-based phase selection is used for both fast
and delayed tripping. To achieve fast tripping, scheme
communication is required. Delayed tripping does not
require scheme communication. It is possible to permit
delayed tripping only upon failure of the
communications channel by blocking the delayed
tripping logic with a communications channel healthy
input signal.
On receipt of the communications signal, phase
selective outputs for fast tripping are set based on the
Line differential protection RED670
1MRK 505 379-BEN N
Hitachi Power Grids 41
© Copyright 2017 Hitachi Power Grids. All rights reserved
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