4.40
SEL-700G Relay
Instruction Manual
Date Code 20170814
Protection and Logic Functions
Group Settings (SET Command)
and neutral third-harmonic voltage may not be equal, and their rates of
increase with increasing load may be different as well. Note also that the third-
harmonic characteristics of generators have been observed to change over
time, perhaps because of modifications to auxiliary equipment connected to
the generator bus. After such modifications, repeat the commissioning
procedure and adjust the settings of the element.
The 64RAT setting is calculated to balance the voltage differential element
performance over the range of machine loading. To properly set this element
for an individual generator, operate the generator at full load and no load
outputs, use the relay METER command to record the measured third-
harmonic voltages, then calculate the settings. Details of this procedure are
provided in the following text. More elaborate procedures using the third
harmonic measurements at several load outputs and varying power factors can
be found in the SEL Application Guide AG2005-08, Setting 100% Stator
Ground Fault Detection Elements in the SEL-300G Relay, available on the
SEL website. This guide is written for the SEL-300G, but it can be adapted for
the SEL-700G.
You can apply the Zone 2 stator ground element as a neutral third-harmonic
undervoltage element. When you set 64RAT := 0.0, the relay disables the
third-harmonic voltage differential function. Setting 64G2 acts as a neutral
third-harmonic undervoltage element (27N3) with voltage pickup defined by
64G2P.
When open-delta generator PTs are applied (DELTAY_X := DELTA) and an
external zero-sequence voltage (3V0) is connected to the
VS
input
(EXT3V0_X := VS), the relay allows you to program 64G2 as a third-
harmonic voltage differential element or a neutral third-harmonic
undervoltage element. On the other hand, when open-delta generator PTs are
applied and no external 3V0 is brought in (EXT3V0_X := NONE), the relay
allows you to program 64G2 only as neutral third-harmonic undervoltage
protection.
Note: If EXT3V0_X := VN, then the 64G element is disabled.
The 64G1P setting defines the sensitivity of the relay fundamental frequency
neutral overvoltage element used to detect stator ground faults in the middle
and upper areas of the generator winding. The 64G1D setting defines the
Zone 1 element time delay.
The 64G2P setting defines the sensitivity of the relay third-harmonic voltage
differential function used to detect stator ground faults in the lower and upper
areas of the generator winding. The 64RAT setting defines a balancing ratio
used to provide consistent element performance over the range of machine
operation. The 64G2D setting defines the Zone 2 element time delay.
Setting 64RAT is hidden and set to 0.0 when setting DELTAY_X := DELTA
and EXT3V0_X := NONE.
The 64G1TC torque-control setting disables Zone 1 when its result is logical 0
and enables Zone 1 when its result is logical 1. Setting 64G2TC works
similarly for Zone 2.
Table 4.6
Stator Ground Protection Settings
(Sheet 1 of 2)
Setting Prompt
Setting Range
Setting Name :=
Factory Default
64G PROT EN
Y, N
E64G := Y
NEUTRAL O/V LVL
OFF, 0.1–150.0 V
64G1P := 5
Содержание SEL-700G Series
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