P92x/EN GS/E11 Technical Guide
Getting Started
Page 4/18 MiCOM P921-P922-P923
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If you are making measurements on the internal electronic circuitry of an equipment
in service, it is preferable that you are earthed to the case with a conductive wrist
strap. Wrist straps should have a resistance to ground between 500kW – 10MW.
If a wrist strap is not available you should maintain regular contact with the case to
prevent a build-up of static. Instrumentation which may be used for making
measurements should be earthed to the case whenever possible.
More information on safe working procedures for all electronic equipment can be
found in BS5783 and IEC 147-OF. It is strongly recommended that detailed
investigations on electronic circuitry or modification work should be carried out in a
special handling area such as described in the above-mentioned BS and IEC
documents.
3. RELAY MOUNTING
Relays are dispatched either individually or as part of a panel/rack assembly.
If an MMLG test block is to be included it should be positioned at the right-hand side
of the assembly (viewed from the front). Modules should remain protected by their
metal case during assembly into a panel or rack.
For individually mounted relays an outline diagram is supplied in chapter 2 of this
Technical Guide showing the panel cut-outs and hole centres.
4. UNPACKING
Care must be taken when unpacking and installing the relays so that none of the
parts is damaged or the settings altered. Relays must only be handled by skilled
persons. The installation should be clean, dry and reasonably free from dust and
excessive vibration. The site should be well lit to facilitate inspection. Relays that have
been removed from their cases should not be left in situations where they are
exposed to dust or damp. This particularly applies to installations which are being
carried out at the same time as construction work.
5. STORAGE
If relays are not to be installed immediately upon receipt they should be stored in a
place free from dust and moisture in their original cartons. Where de-humidifier bags
have been included in the packing they should be retained. The action of the de-
humidifier crystals will be impaired if the bag has been exposed to ambient
conditions and may be restored by gently heating the bag for about an hour, prior to
replacing it in the carton.
Dust which collects on a carton may, on subsequent unpacking, find its way into the
relay; in damp conditions the carton and packing may become impregnated with
moisture and the de-humifier will lose its efficiency.
Storage temperature : –25°C to +70°C.
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