Function Range or value Accuracy
Operate time, alarm 1.00 s typically at R
f
= 0 Ω
and filter length = 1 s
-
Trip time, trip 3.00 s typically at R
f
= 0 Ω
and filter length = 1 s
-
Alarm time delay (0.00 - 600.00) s Less than 2.00 s (±0.2% or ± 2.00 s, whichever
is greater) at R
f
= 0 Ω and filter length = 1 s
7.14 100% stator earth fault protection, injection based
STTIPHIZ (64S)
GUID-168591A0-89CC-4F8B-8B7C-C0CDEAF2DD4B v1
7.14.1 Identification
GUID-949F59D4-5AD5-40D9-B275-3542517C988F v1
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
100% stator earth fault protection,
injection based
STTIPHIZ Rse< 64S
7.14.2 Functionality
GUID-A9BF9D69-2179-441C-A6C7-69EF0F55DD61 v3
The 100% stator earth-fault protection (STTIPHIZ (64S)) is used to detect ground faults in the
stator windings of generators and motors. STTIPHIZ (64S) is applicable for generators connected
to the power system through a unit transformer in a block connection. An independent signal with
a certain frequency different from the generator rated frequency is injected into the stator circuit.
The responce of this injected signal is used to detect stator ground faults.
To implement the above concept, a separate injection box is required. The injection box generates
a square wave voltage signal which for example can be fed into the secondary winding of the
generator neutral point voltage transformer or grounding transformer. This signal propagates
through this transformer into the stator circuit.
The magnitude of the injected voltage signal is measured on the secondary side of the neutral
point voltage transformer or grounding transformer. In addition, the resulting injected current is
measured through a resistive shunt located within the injection box. These two measured values
are fed to the IED. Based on these two measured quantities, the IED determines the stator
winding resistance to ground. The resistance value is then compared with the preset fault
resistance alarm and trip levels.
When the synchronous machine is at standstill, the protection function can not only detect the
ground fault at the generator star point, but also along the stator windings and at the generator
terminals, including the connected components such as voltage transformers, circuit breakers,
excitation transformer and so on. The protection function is fully operative in all operating
conditions when stable measurements are achieved. Both function STTIPHIZ and ROV2PTOV shall
be configured and shall operate in parallel in the same REG670 in order to perform the 100% stator
earth-fault protection function. The function STTIPHIZ performs the earth-fault protection based
on the injection principle in order to protect the section of the stator windings close to the
generator neutral point; the function ROV2PTOV performs the standard 95% stator earth-fault
protection based on the neutral point fundamental frequency displacement voltage.
1MRK 502 066-UUS B Section 7
Impedance protection
409
Technical manual
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