0User manual

0MV vacuum circuit breaker

0Evolis Merlin Gerin 024 kVEarthing truck

02005

1 Schneider Electric 07897591EN REV.A0

0Earthing truck (cmalt) operation

FunctionThe earthing truck has the function of connecting the busbars in one half-switchboard to earth. Naturally, the earthing operation must be carried out when de-energised so as not to create a short-circuit.

InterlockingIn order to de-energise a half-busbar in complete safety, it is necessary to use a key centre. This centre enables the operator to ensure that all of the circuit breakers are racked out in the half-switchboard to be connected to earth.The operation is carried out in the following manner (in order to earth busbar A, cf. figure 1):b rack out all of the circuit breakers on the half-switchboard, including that of the bus-sectioning cubicle (circuit breakers in cubicles 1 - 2 - 3),b lock these circuit breakers in the “racked out” position and remove the keys which are released (keys D1, D2 and C),b place these three keys in the corresponding key centre and remove the key that is released (STA). This then locks the circuit breaker keys in place,b unlock the earthing truck using the released key, which only enables the truck to be racked in the half-switchboard which has just been de-energised.

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Figure 1: single line diagram example

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D1

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D2 C

C D2 D1 STASTA STB

D5 D6

C D6 D5 STB

Busbar A

AD type feeder cubicle

Earthing truck cmalt Key centre

AD type incomer cubicle

AD type feeder cubicle

AD type incomer cubicle

CL-GL type bus-sectioning cubicle

Busbar B

2Schneider Electric 07897591EN REV.A0

0Earthing truck (cmalt) operation

Mechanism to disable racking of the earthing base in the energised half-switchboardCubicles in a switchboard equipped with an earthing base include a mechanism to avoid incorrect operation. This fool-proof system is different according to whether the cubicle is part of the half-busbar A or B in the switchboard (cf. figure 1). The earthing truck cannot be racked into a cubicle unless the key latch opposite the fool-proof system is lowered using the right key.The fool-proof system is mounted with one screw on the higher hole in cubicles belonging to the half-switchboard on the left hand side (cf. figure 2, safety no. 1), and with one screw on the lower hole in cubicles belonging to the half-switchboard on the right hand side (cf. figure 2, safety no. 2). Two screws are mounted on the bus-sectioning cubicle to make it impossible to rack in the earthing truck (cf. figure 2, safety no. 3).

Figure 2: locking mechanism, front view

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Safety device no. 1: Insertion impossible in the right hand half-switchboard

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Safety device no. 2: Insertion impossible in the left hand half-switchboard

Safety device no. 3: Bus-sectioning cubicle, impossible to insert the earthing truck

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STB

STA

CradleEarthing base

STA

STB

Earthing base

STA

STB

Earthing base

Cradle

Cradle

3 Schneider Electric 07897591EN REV.A0

0Earthing truck (cmalt) operation

OperationOnce the truck is unlocked, the sequence of operations is as follows:b insert the earthing truck in one of the cubicles of the de-energised half-switchboard,b rack-in the device with the door open,b manually charge the spring using the handle,b close the contacts of the earthing truck (press on the closing button).

When the earthing base is closed, a padlockable runner enables access to the opening button to be disabled, and thus enables the earthing truck to be locked in the closed position.Moreover, an interlock disables the possibility of racking the earthing truck out when it is closed (as for a circuit breaker). The earthing of busbars can therefore be made secure using padlocks (three padlocks at most).

When the earthing truck is open, this same runner also enables padlocked disabling of access to the closing button. In this position, racking out is possible.

These features should enable an earthing truck to be correctly installed and used on conventional switchboards having only one bus-sectioning cubicle but with an unlimited number of feeder and incomer cubicles.In the case of large switchboards with several bus-sectioning cubicles (i.e. switchboards in which it is not possible to talk in terms of half-switchboards) a specific study is required to adapt the interlocks to the configuration in question.

Electrical characteristicsAn earthing truck exists for each cubicle width.

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Closed Open

cmalt phase distance 230mm

cmalt phase distance 250mm

Un kV 24 24insulation voltage U impulse 125 125

power frequency 50 50making capacity kA 25 31.5

k 65 82

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07897591EN - REV. A0 04/2005

The Schneider group service centres are at your service for:engineering and technical assistancecommissioningtrainingpreventive and corrective maintenanceadaptationspare parts.Contact your sales representative who will put you in touch with your nearestSchneider group service centre or call us on 33 (0)4 76 57 60 60(Grenoble, France).

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As standards, specifications and designs change from time to time, please ask for confirmation of the information given in this publication.

This document has been printed on ecological paper.

Design: Technical documentation department Medium Voltage, Varces (38), France