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6.10 Extension Cubicles
Type 298 equipment is designed to allow extension cubicles to be fitted as required to either end of the switchboard. The following procedure describes the work that needs to be carried out.
De-energise the busbars in full accordance with the site shutdown and permit to work requirements
Remove the panel end covers on the existing switchboard
If extending on the right hand end: Remove the busbar insulation barrier and replace with appropriate half high or cut-out barrier.
If extending on the left hand end: Remove the busbar insulation barrier and dispose of as the appropriate on is already fitted to the extension tier.
Move the extension cubicle(s) onto the prepared foundations in the order detailed on the revised General Arrangement drawing. Movement can be accomplished using floor rollers (maximum diameter 12mm) between the cubicle base plate and the site floor.
Ensure each section is correctly positioned relative to the neighbouring cubicle. It is essential to ensure correct alignment of the front face of the switchboard.
Bolt the cubicles together, noting that the insulation retaining strips are to be positioned between the cubicles to provide partitioning between compartments.
Fasten the extension cubicle(s) to the foundation fixings.
Open the rear cable chamber door of the outer most cubicle on the originally installed Switchgear.
Remove the vertical bus bar chamber cover.
Remove the bolted end plate from within the bus bar chamber to expose the bus bar aperture into the extension cubicle.
Fit the extension bus bars & busbar seals.
Re-fit the bolted end plate internally within the outer most bus bar chamber cubicle.
Replace all vertical bus bar chamber covers and close the rear cable chamber doors.
Re-fit the insulation barriers (if required) and end covers on the outer most cubicle ends.
Re-commission the bus bar system in accordance with Section 7 Pre-Commissioning of this manual.
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7 Pre-Commissioning 7.1 Overview
For the purpose of this manual, the term “Pre-Commissioning” refers to the work that is carried out to ensure that the equipment operates as per the contract requirements. This includes post-installation testing and the set-up of equipment such as protection relays in order that they functionally operate as intended by the electrical schematics.
More detailed commissioning work that concerns the detailed operation of the plant is not covered by this document
It is recommended that all pre-commissioning work is carried out by Powell UK personnel and also that Powell UK personnel assist with the detailed commissioning work. Please contact the Site Services team for further
information regarding both pre-commissioning and commissioning personnel and site activities.
7.2 Pre-connection Checks
In preparation for pre-commissioning, the following work should be carried out prior to connection of the high-voltage power supply:
7.2.1 General and Visual Checks
Check the general condition of the switchgear for damage of any kind.
Remove all material residues, foreign bodies and tools from the switchgear.
Clean the switchgear, rubbing down insulating parts with a clean, soft, non-fraying dry cloth.
Remove greasy or adhesive dirt with a cloth dampened with a slightly alkaline household cleaner.
Wash off with clean water and dry carefully.
Perform a visual examination of the withdrawable elements, power modules, isolating contacts, insulating parts etc.
For systems with a BIL of 95kV, check the correct fit and location of the additional parts required to ensure compliance with the rated insulation level of switchgear panels, in line with the contract documentation.
Visually check the connection of the main earthing bar to the station earthing conductor.
Check all busbar connections have been torqued to the correct level.
Check all busbar joints have been fitted with appropriate boots and shrouds.
7.2.2 Control Wiring Completion Checks
Carry out a point-to-point wiring check of the tier interconnection wiring.
Ensure all connections are tight and that the cable marker is visible.
7.2.3 Low Ohm (Ducter) Tests (Minimum 50A)
Perform a Low Ohm test through all closed and connected circuit breakers.
Perform a Low Ohm test through all closed and connected mechanically operated earth switches.
Perform a Low Ohm test through all busbars.
7.2.4 Primary Injection Tests
Perform a primary injection test on the current transformers.
Perform a primary injection test on the voltage transformers.
These tests are optional. Primary injection testing is carried out on all voltage and current transformers in the factory and it is at the client’s discretion whether these tests should be carried out again on site.
7.2.5 Secondary Injection Tests
Perform a secondary injection test on all protection relays.
Perform a secondary injection test on all metering relays.
Note: Test voltage must match the system voltage
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7.2.6 Power Frequency Pressure (Flash) Tests
Perform flash test on all circuit breakers.
Perform flash test on all voltage transformers.
Perform flash test on all current transformers.
Perform flash test on switchboard.
7.2.7 Insulation Resistance Tests (Minimum 5kV)
Perform insulation resistance test on all circuit breakers.
Perform insulation resistance test on all voltage transformers.
Perform insulation resistance test on switchboard.
7.2.8 Electro-Mechanical and Functional Checks
Turn on the auxiliary and control voltage.
Carry out test operations of switching devices manually or by electrical control, and simultaneously observe the relevant position indicators.
Check mechanical and electrical interlocks for effectiveness, without using force. Please refer to Section 9.4 Electro-Mechanical Interlock Checks for further details.
Set the protective devices in the switchboard to the required values and check their function with test equipment.
7.2.9 Protection Relays
Configure protection settings in protection relays
Configure control and functional settings in protection relays
Configure communications settings in protection relays if required.
7.2.10 Final Checks
Following completion of checks and tests, ensure that:
All test equipment and tools are removed from the switchroom or sub-station.
All temporary connections are removed and permanent connections are reinstated.
All covers removed to facilitate testing are reinstated.
All test results are documented on appropriate test sheets.
7.3 Energisation
The following procedure describes the connection of the switchboard to the 3 phase mains power. Please note that this activity is normally undertaken by the client with the assistance and supervision of our Site Services Personnel. The following description serves only to provide an idea of what is required and a detailed procedure provided by the client will take precedence over this.
Ensure that the circuit breakers in the switchboard are in the OFF position.
Remove any existing earthing and short circuiting connections in the critical switching area.
Energise the feed cables.
Connect the switchgear step-by-step, observing the signals and indicators.
Check the conductors are in phase as far as necessary when several incoming feeder cables and switchgear sections are connected.
Carry out all measurements and check all functions dependent on the high-voltage power supply being connected.
Pay careful attention to irregularities of any kind.
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7.4 Standard Tools
Standard tools that are supplied on each contract are as detailed below. Please refer to contract documentation for any other special tools that may be supplied.
VCB Service Trolley
VCB Racking Handle
Door Handle/Rear Cover Handle
Earth Switch Handle
Busbar Earth Truck Extension Rod
VT Ramp
Manual Charging Handle
7.5 Special Tools
Special tools that can be supplied if a requirement of the contract are detailed as below. Please refer to contract documentation for details.
Loose items that are supplied on each contract are as detailed below. Please refer to contract documentation for any other loose items that may be supplied.
Cubicle Fixing Bolts
Busbar Fixing Bolts
Neoprene gasket
7.7 Lubricants and Cleaning Agents
Contact Lubricant - Contact Treatment Grease (For VT Contacts) RS Components Ltd – Part No 503-335
Mobile Grease 28 (For Breaker Primary Contacts) Mechanical Lubricant - Rocol MTS 1000 (For Tier)
RS Components Ltd – Part No. 691-397 Rheolube 368A (For Breaker)
Contact Cleaner - Electrical Cleaner
RS Components Ltd – Part No 203-0750 Insulation Cleaner - Electro Mech.
RS Components Ltd – Part No 268-2115
If RS Components Ltd products are not available locally, please contact Powell UK for an approved equivalent supplier.
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8 Operation of the VCB Cubicle
8.1 Insertion and Withdrawal of the Circuit Breaker
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Figure 16 Circuit Breaker Operation
8.1.1 Insertion
The circuit breaker is inserted into the switchgear cubicle with the use of a service trolley (a service trolley is provided for each cubicle width). The procedure for inserting the circuit breaker is as follows:
Unlock and open the compartment door.
Position the service trolley (with the breaker on) at the correct height facing the panel front. The height of the trolley may need some adjustment and this can be done by winding the trolley adjusters up or down the threaded bar as required.
Move the trolley up to the cubicle and ensure that it automatically latches to the cubicle such that it can’t be moved away.
Operate the anti-rollout lever to release the breaker from the trolley.
Move the breaker forwards until it is fully inside the cubicle and the anti-rollout lever has latched onto the anti-rollout bracket on the compartment mid pan.
The breaker is now inserted into the compartment and is in the “Test/Isolated” position.
Remove the breaker control wiring plug (secondary disconnect) from the storage position on the breaker and connect it to the socket on the top of the compartment above the breaker.
Detach the trolley from the cubicle by moving the lever on the trolley (at the front and underneath the bench top) to the right and pulling the trolley away.
Close and lock the compartment door. The breaker can now be racked into the “In Service” position using the provided racking handle assuming all other interlocks will allow it.
Fit the racking handle to the hexagonal spigot of the racking mechanism through the access hole in the compartment door.
Turn the handle clockwise until the stop is reached. It will take approximately 20 turns to achieve this.
NOTE: The circuit breaker must not be stopped at any position in the travel range between the “Isolated”
position and the “In Service” position.
Remove the racking handle.
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8.1.2 Withdrawal
The circuit breaker is removed from the switchgear cubicle with the use of a service trolley (a service trolley is provided for each cubicle width). The procedure for withdrawal of the circuit breaker is as follows:
Ensure that the circuit breaker is open.
Fit the racking handle to the hexagonal spigot of the racking mechanism through the access hole in the compartment door.
Turn the handle anti-clockwise until the stop is reached. It will take approximately 20 turns to achieve this.
NOTE: The circuit breaker must not be stopped at any position in the travel range between the “In Service”
position and the “Isolated” position.
Unlock and open the compartment door ensuring that the door retaining catch is disengaged before opening.
Disconnect the breaker control wiring plug (secondary disconnect) from the socket on the top of the compartment above the breaker and attach it to the storage position on the breaker.
Position the service trolley at the correct height facing the panel front. The height of the trolley may need some adjustment and this can be done by winding the trolley adjusters up or down the threaded bar as required.
Move the trolley up to the cubicle and ensure that it automatically latches to the cubicle such that it can’t be moved away.
Operate the anti-rollout lever to release the breaker from the cubicle.
Move the breaker backwards until it is completely on the service trolley and the anti-rollout lever latches on the trolley.
Detach the trolley from the cubicle by moving the lever on the trolley (at the front and underneath the bench top) to the right and pulling the trolley away.
The breaker is now completely removed from the compartment.
8.2 Test/Isolated Position
This is the position in which the breaker can be operated without actually energising the bus and is used for testing and commissioning purposes. When in the “In Service” position, the breaker will operate and energise/de-energise the bus.
When in this position it is possible to open the compartment door and manually open and close the breaker using the Close/Trip button and to manually charge the breaker using the handle provided. A remote Open and Close (if configured) will also operate the breaker in this position. For commissioning purposes a temporary supply will be used to allow closure of the VCB to be tested.
This is the position from which it is also possible to completely remove the breaker from the cubicle.
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8.3 Interlocks
A series of mechanical and electro-mechanical interlocks are provided to prevent mal operation of the breaker that could result in damage to the equipment or be dangerous to the operating personnel. These are as follows:
General Interlocks
Key Interlocks
8.3.1 General Interlocks
These are a series of mechanical interlocks that are provided as standard to:
Ensure that the compartment door can only be opened when the breaker is in the “Test/Isolated Position”
or completely removed from the cubicle.
Prevent the breaker being racked into the “In Service” position with the door open.
Prevent the breaker from being operated when the door is open unless it has been racked into the
“Test/Isolated Position”.
Ensure that the breaker cannot be closed unless it is racked into either the “Test/Isolated” or “In Service”
position.
Ensure that the earthing switch cannot be closed when the breaker is in the “In Service” position.
There is also a series of mechanical interlocks that are provided via the Interlock Box (located under the VCB door) and these are detailed below:
Figure 17 Interlock Box
Prevent breaker from being racked from the “Test/Isolated position to the “In Service” position.
Ensure that the breaker cannot be racked to the “In Service” position when the earthing switch is closed.
Prevent access to the earthing switch operating mechanism. This is done by blocking off the access hole for the earth switch handle (see Figure 17 Interlock Box) using the padlock knob or key switch. Please note that this is entirely operator-driven and is controlled only by turning the padlock knob or key switch and padlocking it in the required position.
The following procedure details how to rack the breaker in and out of service.
Ensure the breaker is in the “Test/Isolated” position or is completely removed from the cubicle.
Full depress push rod.
Turn the key or wing knob (depending what has been ordered on the contract)
Remove key (if supplied).
It is now not possible to rack the breaker to the “In Service” Position.
Please refer to the following section for further details regarding key interlocks
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8.3.2 Key Interlocks
If required, a key interlocking system can be provided. This inhibits busbar earthing unless all incoming sources are isolated. This section details some of the options in terms of operation but please refer to contract
documentation for exact details of the operation of this system.
A series of keys can be used to prevent actions being undertaken unless certain other conditions have first been met. An example of this is busbar earthing. For example, in order to earth Bus A, Incomer A and the Bus Tie must be racked out and the racking interlock applied. This ensures that the busbar earth switch cannot be racked onto a live bus. This frees those 2 keys which then go onto an exchange box to release the busbar earth racking interlock key.
Key Free Off
If a key free off system is selected, it means that access to the circuit earth switch is normally blocked. The key for this is held elsewhere (usually upstream). When the upstream breaker has been isolated then the key can be removed and placed in the interlock box. This in turn allows access to the key for the circuit earth switch and traps the key from the upstream breaker, thus preventing it from being re-energised.
Key Free On
If a key free on system is selected, it means that the key which is normally trapped can only be removed when the circuit earth switch is applied. Once applied, the key can then be removed and taken to a downstream breaker (as detailed in the Key Free Off description above) or a transformer house.
8.4 Operating Mechanism
The circuit breaker is fitted with a spring charging handle and open/close buttons on the front of the breaker.
These can only be operated with the door open, which means that the breaker must be in the “Test/Isolated”
position. A mechanical “push to trip” button can be fitted to the door if required to allow a local “Trip” command in the “In Service” position.
Once the breaker is closed, the spring discharges and needs to be re-charged before another close operation can be actioned. This is achieved via a motor charged spring charging mechanism which is fitted to the circuit breaker to enable the spring to automatically recharge following a close operation. This can also be done manually using the charging handle on the front of the breaker when the breaker is in the “Test/Isolated” position. Mechanical indicators show “Spring Charged” or “Spring Discharged” status.
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8.5 Earthing Switch
The circuit earthing switch is located in the cable chamber has an independent manual closing mechanism which is operated using the earth switch handle via the access hole in the interlock box on the front of the cubicle (refer to Figure 17 Interlock Box). There is a user-operated mechanical interlock on the interlock box that blocks off the access hole when the padlockable knob is turned. This prevents the earth switch handle from being inserted and would be mainly used when the breaker is in the “Test/Isolated” position or completely removed from the cubicle.
An automatic mechanical interlock ensures that the earthing switch cannot be operated when the breaker is in the
“In Service” position.
Figure 18 Earthing Switch Operation The procedure for closing the earthing switch is as follows:
Ensure the breaker is in the “Test/Isolated” position or completely removed from the cubicle.
Ensure the door is closed.
Ensure the padlock has been removed from the padlockable knob and turned such that the access hole is clear.
Insert earthing switch handle such that it engages with the hexagonal shaft of the switch itself.
Turn the handle anti-clockwise through approximately 180° until the stop is reached. Complete the
Turn the handle anti-clockwise through approximately 180° until the stop is reached. Complete the