Mounting and Commissioning
3.1 Mounting and Connections
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
363
Example:
Summation current transformer 60 A / 1 A
Matching factor for sensitive earth fault current detection: FACTOR IEE2 = 60 (if the input on side 2 is used)
If the sensitive current input of side 1 is used for rotor earth fault current detection (see Appendix A.3), FACTOR
IEE1 = 1 is selected.
In Figure „Busbar System“ in Appendix A.3 the generator starpoint has a low-resistance earthing. To avoid cir-
culating currents (3rd harmonic) in multi-generator connections, the resistor should be connected to only one
generator. For selective earth fault detection, the sensitive earth fault current input I
EE2
is looped into the
common return line of the two sets of CTs (current differential measurement). The current transformers are
earthed in one place only. FACTOR IEE2 is set to 1. Balanced DE current transformers (winding balance) are
recommended for this type of circuit.
In Figure „Block Connection“ with isolated starpoint in Appendix A.3 earth fault detection uses the displacement
voltage. A load resistor is provided on the broken delta winding to avoid spurious tripping during earth faults in
the power system. The UU
E
input of the device is connected via a voltage divider to the broken delta winding
of an earthing transformer (address 223 UE CONNECTION = broken delta). Factor 225 Uph / Udelta is
determined by the transformation ratio of the secondary-side voltages:
The resulting factor between the secondary windings is 3/√3 = 1.73. For other transformation ratios, e.g. where
the displacement voltage is measured using an inserted CT set, the factor must be modified accordingly.
Factor 224 FACTOR UE considers the full transformation ratio between the primary voltage and the voltage
fed to the device terminals, i.e. it includes the voltage divider that is connected upstream. For a primary nominal
transformer voltage of 6.3 kV, a secondary voltage of 500 V with full displacement and a voltage divider ratio
of 1:5, this factor would be for example
In Figure „Block Connection with neutral transformer“ in Appendix A.3, a load resistor connected to the gener-
ator starpoint reduces the interference voltage from network-side earth faults. The maximum earth fault current
is limited to approx. 10A. The resistor can be a primary or secondary resistor with neutral transformer. The
neutral transformer should have a low transformation ratio to avoid a small secondary resistance. The resulting
higher secondary voltage can be reduced by a voltage divider. Address 223 UE CONNECTION is set to neutr.
transf..
The Figure „Startup Earth Fault Protection“ in Appendix A.3 shows the connection of the DC voltage protection
for systems with startup converter. The amplifier 7KG6 amplifies the signal measured at the shunt to a
maximum of 10 V or 20 mA, depending on the equipment. Input TD1 can be adapted to the type of signal (volt-
age or current) by means of wire jumpers (see also 3.1.2 "Switching Elements on Printed Circuit Boards").
Figure „Rotor Earth Fault Protection“ in Appendix A.3 shows in an exemplary way how the rotor earth fault pro-
tection is connected to a generator with static excitation. The earthing must be connected to the earthing brush.
The coupling device 7XR61 must be extended by the external resistors 3PP1336 if the circulating current can
exceed 0.2 A due to the 6th harmonic component in the excitation voltage. This can be the cause with excitation
voltages UU
Exc
above 150 V. The I
EE 1
input evaluates the earth fault current flowing between the rotor and the
ground as a result of injecting a voltage into the rotor circuit. The matching factor FACTOR IEE1 is set to 1.
Figure „Voltage Transformer Connections for Two Voltage Transformers in Open Delta Connection (V Connec-
tion)“ in Appendix A.3 shows how a connection is made with only two system-side voltage transformers in open
delta connection (V connection).
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