218
1MRS751802-MUM
Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
11.4.2.
Measurements
Following measurements are supported in this application example:
• True RMS measurement of phase currents
• True RMS measurement of neutral current
• True RMS measurement of phase-to-phase voltages
• True RMS measurement of residual voltage
• Fundamental frequency active power [kW]
• Fundamental frequency reactive power [kVAr]
• Fundamental frequency displacement power factor cos (
φ
)
• Power factor PF including harmonics
• Fundamental frequency active energy [kWh]
• Fundamental frequency reactive energy [kvarh]
• System frequency measurement
11.4.3.
Measurement connections
The three-phase current, neutral current transformers and residual voltage
transformer are connected to the connector X1.1 on the rear panel. The rated currents
of the measuring input are 1 A and 5 A and additionally, for earth fault, 0.2 A and 1
A. The rated values for voltage are 100 V, 110 V, 115 V and 120 V.
In this application two neutral current measurements are used. The neutral current
I
0b
measured by a cable transformer is used for directional earth fault protection and
the neutral current I
0
measured by the sum connection of the phase current
transformers is used for non-directional earth fault protection.
The technical data of the current transformers and the voltage transformer are set via
the Relay Setting Tool or the local HMI. The settings can be found in
Main menu\Configuration\Meas. devices\
.
Refer to
REX 521 Technical Reference Manual, General
(see Section 1.5. Related
documents) for further information about how to set the rated currents and voltage.
11.4.4.
Protection
All the necessary settings for the protection functions can be set via the Relay
Setting Tool or the local HMI. The settings can be found in
Main menu\Protection\
.
The overcurrent, the phase discontinuity and thermal overload protection can be
implemented in the same way as in the first application example Section 9.1.
Outgoing feeder, Basic B01, and the directional earth fault protection as in the fifth
application example Section 10.1. Outgoing feeder, Medium M01.
11.4.4.1.
Non-directional earth fault protection
A double earth fault occurs when two phase-conductors get in galvanic connection
with the earth. This can occur in the same line or between two lines when the fault
current has to flow through the earth. This fault type is also known as a cross-country
fault.
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