P92x/EN CM/E11
Techncal Guide
Commissioning Guide
Page 26/28
MiCOM P921-P922-P923
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8.2.4
Measurement accuracy
If the power system is energised, the values measured by the relay can be compared
with known system values to check that they are in the approximate range expected. If
they are then the analogue/digital conversion and calculations are being performed
correctly by the relay. Suitable test methods can be found in Section 6 of this chapter.
Alternatively, the values measured by the relay can be checked against known values
injected into the relay via the test block, if fitted, or injected directly into the relay
terminals. Suitable test methods can be found in Section 7 of this chapter. These tests
will prove the calibration accuracy is being maintained.
8.3
Method of repair
If the relay should develop a fault while energised, depending on the nature of the
fault, the watchdog contacts will change state and an alarm will be generated. Due to
the use of surface-mount components, faulty PCBs should be replaced as it is not
possible to perform repairs on damaged circuits. Thus either the complete relay or
just the faulty PCB, identified by the relay’s diagnostic software, can be replaced.
Refer to Chapter P92x/EN FT of this Technical Guide for more information on alarms.
The preferred method is to replace the complete relay as it ensures that the internal
circuitry is protected against electrostatic discharge and physical damage at all times
and overcomes the possibility of incompatibility between replacement PCBs. However,
it may be difficult to remove an installed relay due to limited access in the back of the
cubicle and rigidity of the scheme wiring: to avoid such difficulties, the MiCOM P921-
P922-P923 relays are designed to be removed while energised for fast replacement
of the live part of the relay, thus minimising the absence of protection.
BEFORE CARRYING OUT ANY WORK ON THE EQUIPMENT, THE USER SHOULD BE
FAMILIAR WITH THE “SAFETY” SECTION OF CHAPTER “P92x/EN IN”, OF THIS
MANUAL. THIS SHOULD ENSURE THAT NO DAMAGE IS CAUSED BY INCORRECT
HANDLING OF THE ELECTRONIC COMPONENTS.
8.3.1
Replacing the complete relay
The MiCOM P921-P922-P923 relays can be removed and replaced if necessary
without having to disconnect the rear terminals.
This is possible while the relay is energised. It is however recommended that all
auxiliary supplies are isolated before working on the relay.
Summary of Contents for MiCOM P921
Page 1: ...MiCOM P921 P922 P923 Voltage and Frequency Relays Technical guide P92x EN T E11...
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Page 4: ...P92x EN T00 E11 Technical Guide Content Page 2 2 MiCOM P921 P922 P923 BLANK PAGE...
Page 5: ...Technical Guide Px2xx EN SS A11 SAFETY SECTION SAFETY SECTION...
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Page 8: ...Px2xx EN SS A11 Technical Guide SAFETY SECTION Page 2 6 BLANK PAGE...
Page 12: ...Px2xx EN SS A11 Technical Guide SAFETY SECTION Page 6 6 BLANK PAGE...
Page 13: ...Technical Guide P92x EN GS E11 MiCOM P921 P922 P923 aBCD Getting Started...
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Page 16: ...P92x EN GS E11 Technical Guide Getting Started Page 2 18 MiCOM P921 P922 P923 aBCD BLANK PAGE...
Page 33: ...Technical Guide P92x EN CO E11 MiCOM P921 P922 P923 aBCD Connection Diagrams...
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Page 45: ...Technical Guide P92x EN TD E11 MiCOM P921 P922 P923 Technical Data...
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Page 76: ...P92x EN TD E11 Technical Guide Technical Data Page 30 30 MiCOM P921 P922 P923 BLANK PAGE...
Page 77: ...Technical Guide P92x EN FT E11 MiCOM P921 P922 P923 User Guide...
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Page 258: ...P92x EN CT E11 Technical Guide Courier Database Page 68 118 MiCOM P921 P922 P923 BLANK PAGE...
Page 296: ...P92x EN CT E11 Technical Guide Courier Database Page 106 118 MiCOM P921 P922 P923 BLANK PAGE...
Page 298: ...P92x EN CT E11 Technical Guide IEC 60870 5 103 Page 108 118 MiCOM P921 P922 P923 BLANK PAGE...
Page 308: ...P92x EN CT E11 Technical Guide IEC 60870 5 103 Page 118 118 MiCOM P921 P922 P923 BLANK PAGE...
Page 309: ...Technical Guide P92x EN IN E11 MiCOM P921 P922 P923 abcd Installation...
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Page 312: ...P92x EN IN E11 Technical Guide Installation Page 2 10 MiCOM P921 P922 P923 abcd BLANK PAGE...
Page 319: ...P92x EN IN E11 Technical Guide Installation Page 10 10 MiCOM P921 P922 P923 abcd BLANK PAGE...
Page 320: ...Technical Guide P92x EN CM E11 MiCOM P921 P922 P923 abcd Commissioning Guide...
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Page 351: ...Technical Guide P92x EN RS E11 MiCOM P921 P922 P923 Test Report...
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Page 354: ...P92x EN RS E11 Technical Guide Test Report Page 2 22 MiCOM P921 P922 P923 BLANK PAGE...
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