Switchgear .1 Construction

Switchgear accessible for authorized persons only shall at least comply with accessibility type “A” of IEC publication 62271-200.

In public accessible spaces switchgear of accessibility type “B” shall be used. Besides this measures against unauthorised operation shall be provided.

D.2.1.1 Medium-voltage switchboards shall have metal clad enclosures which are fully partitioned and closed on all sides.

Switchgear supplying secondary essential or non-essential equipment may be of metal enclosed type.

Incorporated low-voltage compartments for control and monitoring systems shall be separated from the medium-voltage compartments in such a way as to render impossible any contact with parts having a rated supply voltage of more than 1000 V.

D.2.1.2 Fully partitioned switchboards

All sections of a fully partitioned, air-insulated medium-voltage switchboard shall be partitioned with re-spect to each other and the surroundings so that they are arc-resistant. Continuous busbar compartments or switch compartments are inadmissible.

Each panel shall be subdivided into at least three arc resistant, partitioned function compartments: the terminal compartment, the switch compartment and the busbar compartment.

D.2.1.3 Partly partitioned switchboards

If the main medium-voltage switchboard is subdivided into two independent and autonomous installations, a continuous busbar compartment is permissible, provided that a protection system (arc monitor, busbar differential protection) is installed which detects internal faults and isolates the affected part of the installa-tion within 100 ms, respectively accidental arcing is reliable prevented by design measures (e.g. solid insu-lated busbar systems).

D.2.1.4 Switchboards supplying primary essential consumers shall have the service continuity LSC 2 according to IEC publication 62271-200.

Section 8 Medium-Voltage Installations

D.2.1.5 Evidence shall be provided that medium-voltage switchboards have passed a type test ac-cording to IEC publication 62271-200. A modification of the construction of a switchboard requires re-testing. The same applies to modifications of the gas exhausting system.

D.2.1.6 Where drawout switchgear units are used, the following conditions shall be met:

 Functional testing and maintenance shall be capable of being performed in safety, even when the busbar is live.

 Drawout switchgear units shall be fitted with mechanical interlocking devices effective in the operat-ing and disconnected position. A key interlock is permitted for maintenance purposes.

Drawout switchgear units are to be locked in place in the operating position.

 The fixed contacts for drawout switchgear units are to be so arranged that, in the withdrawn position, the live contact components are automatically covered, or that complete withdrawal is possible only after a cover has been fitted.

D.2.1.7 Doors which give access to medium voltage are to be interlocked in such a way that they can be opened only after closing the earthing switch.

D.2.1.8 It shall be possible to split main medium-voltage switchboards into two sections by means of at least one circuit breaker. This breaker shall be fitted with selective protection. It shall be possible to supply each section from at least one generator.

Duplicated consumers shall be divided up amongst the dividable switchboard sections.

Note

It is recommended that two different, spatially separated main switchboards, coupled via a transfer line, are used.

D.2.1.9 The partitioning of a gas insulated switch-board supplying primary essential equipment shall correspond with the requirements of an air insulated switchboard. Each gas volume shall be monitored.

A pressure drop shall be alarmed. Measures according to manufacturer’s instruction shall be initiated.

D.2.2 Auxiliary systems

D.2.2.1 Where electrical energy and/or mechanical energy is required for the operation of switches, a means of storing such energy which is designed for at least two ON/OFF switching cycles of all the con-nected components shall be provided.

In general tripping due to overload, short circuit or undervoltage shall be independent of any stored elec-trical energy.

If shunt trip coils are used, the continuity of the tripping circuit has to be monitored. When the wire break-age alarm is activated the switching on shall be interlocked. The power supply has to be monitored.

D.2.2.2 Number of energy sources

For the supply of auxiliary circuits two independent uninterruptible power supplies shall be provided . If one of these uninterruptible power supplies fails, the remaining unit shall supply all switchboard sections.

The switch-over to the reserve source of energy shall be automatically and actuate an alarm. One unin-terruptible power supply shall be fed from the emergency switchboard, and the other one from the main switchboard.

D.2.3 Tests

A routine test in accordance with IEC publication 62271-200 shall be performed in the manufacturer’s works in the presence of a GL surveyor.

A functional test of the interlocking conditions, protective functions, synchronization in the various operat-ing modes shall be performed.

A test schedule shall be compiled and submitted for approval.

D.2.3.1 It is recommended that a partial-discharge test be performed in accordance with IEC publica-tion 62271-200 Annex B if organic insulating materials or gas-insulated busbar penetrapublica-tions are used.

D.2.3.2 High-voltage test

A voltage test at power-frequency shall be performed on every switchgear unit.

The value of the alternating withstand voltage shall be selected in accordance with Table 8.4. The dura-tion of the test is 1 minute in each case.

The following tests shall be carried out in every case:

 conductor to earth

 between conductors

For this purpose, each conductor of the main circuit is connected successively to the high-voltage con-nection of the test unit. All other conductors of the main and auxiliary circuits are to be earthed.

Table 8.4 Test voltages for switchgear Rated voltage

[kV]

Test voltage (rms value) AC withstand voltage

[kV]

Impulse test voltage

[kV]

1 - 3.6 3.6 - 7.2

7.2 - 12 12 - 17.5

10 20 28 38

40 60 75 95

The dielectrical tests are to be performed with all switching devices in the closed position, and with all withdrawable parts in the operating position.

Voltage transformers or fuses may be replaced by dummies which simulate the electric field distribution of the high-voltage arrangement.

Overvoltage protection devices may be isolated or removed.

D.2.3.3 Impulse voltage test

An impulse voltage test in accordance with Table 8.4 may be recognized as equivalent to the high-voltage test. The duration of the test comprises 15 successive pulses.

D.2.4 Low voltage main switchgear design

D.2.4.1 If the low-voltage main switchboard is supplied from the medium-voltage system a circuit breaker for the longitudinal separation of the main busbar shall be provided.

The bus bar sections shall be supplied by circuit breakers suitable for isolation.

D.2.4.2 The arrangement of supply- and consumer sections shall be in accordance with Section 5, C.2.

D.2.4.3 The feeder panels of the low-voltage switchboard shall be partitioned with arc-resistant segre-gations.

D.2.4.4 The unsynchronized connection of subnetworks and the feedback on the medium-voltage side shall be prevented by means of interlocking.

D.2.4.5 Parallel operation of ship service transformers is only permissible for short-term load transfer, if also the medium voltage sides of the transformers are connected.

A forced splitting, independent of the automation system shall be provided.

D.2.4.6 After black out of the supply of the main switchboard or a partial black out of bus bar sections in the low voltage main switchgear, the recovery of the power supply shall be performed automatically.

Section 8 Medium-Voltage Installations

D.2.4.7 If the black out of the supply is caused by a short circuit in the low voltage switchboard no automatic recovery shall be carried out.

D.2.4.8 The manual connecting of the stand by supply shall be possible after the acknowledgement of short circuit trip.

D.2.4.9 A stand by alarm shall be triggered, if components, necessary for the automatic recovery, are not available.

D.2.4.10 A switching off of the medium voltage circuit breaker shall cause the opening of the low volt-age circuit breaker.

D.2.4.11 The supply panels shall meet the requirements for generator panels of this Chapter analo-gously.

D.2.4.12 The low voltage supply panels shall be equipped with a voltmeter and an ampere-meter. It shall be possible to display the currents and voltages of all three phases.

D.2.4.13 The operation modes On, Off, Tripped and Ready shall be indicated by signal lights.

D.3 Switchboard equipment