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Installation and commissioning Chapter 12
Commissioning and maintenance of
the fault clearing system
1 Installation and commissioning
The protection relay system is in an "on-guard" situation where they can be inactive for several
years and then suddenly be required to operate within fractions of a second. This means that
maintenance testing with certain time intervals should be performed to detect failures of the pro-
tection IED or the surrounding circuits. This is a complement to the advanced self supervision
in the modern protection IED.
Relays are not expected to deteriorate with usage but extreme conditions such as mechanical
shocks, AC or DC transients, high ambient temperatures, and high air humidity always have a
certain likelihood of causing damages.
Delivered equipment undergoes extensive testing and quality control in the ABB manufacturing
program. All types of IEDs and their integral components have been subject to extensive labo-
ratory testing during the development and design work. Prior to series production of a specific
IED, it is Type tested according to national and international standards. Each individual relay in
normal production is individually tested and calibrated before delivery.
Protection relays installed in an apparatus cubicle shall be checked in various ways before de-
livery. Insulation test (to check for bad wiring) and complete testing of all equipment with in-
jection of currents and voltages is performed.
During the design of the station certain steps shall be taken to limit the risk of failures e.g. all
relay coils are connected to negative potential to earth to prevent contact corrosion due to elec-
trolyte.
Certain circuits are continuously supervised to improve their availability. Examples of such su-
pervisions are:
• Trip circuit supervision
• Protection DC supply supervision
• DC system earth fault supervision
• Busbar protection CT-circuit supervision
Protection relays shall be encapsulated according to environment requirements. In tropical cli-
mates, cubicles are provided with glass-door and ventilation louvres. Heaters for anti-condensa-
tion, often thermostatically controlled are provided. Cubicle power-loss is limited not to exceed
protection IED temperature limits which according to the IEC standard is 55
°C.
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