PRS-7910
PRS-7910 55
11.7 Electrical Installation and Wiring
11.7.1 Grounding Guidelines
In the case of equipment supplied in cubicles, place the cubicles on the foundations that have
been prepared. Take care while doing so not to jam or otherwise damage any of the cables that
have already been installed. Secure the cubicles to the foundations.
Switching operations in HV installations generate transient over voltages on control signal cables.
There is also a background of electromagnetic RF fields in electrical installations that can induce
spurious currents in the devices themselves or the leads connected to them.
All these influences can influence the operation of electronic apparatus.
On the other hand, electronic apparatus can transmit interference that can disrupt the operation of
other apparatus.
In order to minimize these influences as far as possible, certain standards have to be observed
with respect to grounding, wiring and screening.
NOTICE!
All these precautions can only be effective if the station ground is of good quality.
11.7.2 Cubicle Grounding
The cubicle must be designed and fitted out such that the impedance for RF interference of the
ground path from the electronic device to the cubicle ground terminal is as low as possible.
Metal accessories such as side plates, blanking plates etc., must be effectively connected
surface-to-surface to the grounded frame to ensure a low-impedance path to ground for RF
interference. The contact surfaces must not only conduct well, they must also be non-corroding.
NOTICE!
If the above conditions are not fulfilled, there is a possibility of the cubicle or parts of it
forming a resonant circuit at certain frequencies that would amplify the transmission of
interference by the devices installed and also reduce their immunity to induced
interference.
Movable parts of the cubicle such as doors (front and back) or hinged equipment frames must be
effectively grounded to the frame by three braided copper strips (see Figure below).
The metal parts of the cubicle housing and the ground rail are interconnected electrically
conducting and corrosion proof. The contact surfaces shall be as large as possible.
NOTICE!
For metallic connections please observe the voltage difference of both materials
according to the electrochemical code.
The cubicle ground rail must be effectively connected to the station ground rail by a grounding strip
(braided copper).
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