Switchgear maintenance

Code of practice for selection, installation and maintenance of switchgear and controlgear Part 3 Installation 10118 (Part-Ill) 1982 ... 

General guidelines during installation and maintenance of a switchgear or a controlgear assembly 13/384... 

Specification for electrical cable soldering sockets Code of practice for maintenance of electrical switchgear and controlgear for voltages above I kV and up to 36 kV... 

Code of practice for maintenance of electrical switchgear for voltages above 36 kV Speeificiition for voltage regulation and parallel operation of a.c. synchronous generators Methods of testing plastics... 

Inclusion of thermography into a predictive maintenance program will enable you to monitor the thermal efficiency of critical process systems that rely on heat transfer or retention electrical equipment and other parameters that will improve both the reliability and efficiency of plant systems. Infrared techniques can be used to detect problems in a variety of plant systems and equipment, including electrical switchgear, gearboxes, electrical substations, transmissions, circuit breaker panels, motors, building envelopes, bearings, steam lines, and process systems that rely on heat retention or transfer. 

Although it might be tempting to use the "free space" in switchgear, boiler, compressor, and other equipment rooms for the storage of brooms, paint, drawings and manuals, spare parts, and various other utility and maintenance supplies, it is essential to resist such practices. Suitable broom closets, spare parts storerooms, and utility rooms should be constructed for such storage. 

In case of repair or maintenance, a single switchgear compartment will be pneumatically isolated, i.e. the individual protective gas inlet and outlet valves are closed, the isolating switch is set in its OFF position and an (electrical or pneumatical) interlock with the door of the compartment is set off. Thus, the door can be opened to enable access to the internal components. 

Much depends upon the performance required, e.g. accuracy, energy efficiency, standstill and low speed torque control. External equipment such as extra switchgear, controllers, instrumentation and protection is required and this increases the overall cost of the system. Also required will be extra maintenance and stocking of spare parts. 

Cost of fuel and lubricants, operators salary, annual maintenance costs, interest paid on investment in the installation (DG set, accessories, separate shed, electrical switchgear). 

Circuits are controlled by switchgear which is assembled so that the circuit may be operated safely under normal conditions, isolated automatically under fault conditions, or isolated manually for safe maintenance. These requirements are met by good workmanship carried out by electrically skilled persons and the installation of approved British Standard materials such as switches, isolators, fuses or circuit-breakers (IET Regulation 131.1.1). The switchgear must also be non-combustible or housed in a non-combustible cabinet or enclosure (IET Regulation 421.1.200). The equipment belonging to the supply authority is sealed to prevent unauthorized entry, because if connection were made to... 

In the case of rectifying elements, the total installed cost of a thyristor system is usually less than that of one based on diodes. Operating costs also are lower. Maintenance costs, as we saw in Section 8.3.1.2B, are lower because of the use of static, solid-state control devices rather than the mechanical switchgear of a tap changer. Rectification efficiency might be expected to suffer from the loss of part of the sine wave before firing, but this loss usually is comparable to the inefficiencies of the regulating transformers and the saturable reactors in a diode system. 

A switchgear lockout procedure, and the associated locks and keys, are required to ensure that an equipment item released for maintenance or modification is not started without the agreement of the person to whom it was released, and to confirm that the item is ready for operation. 

A preventive maintenance plan should be conducted for aU plant switchgear. Normal maintenance includes checking and tightening cable connections, testing air circuit-breaker operations, and checking relay and meter caUbrations. 

Advice on the maintenance of high voltage switchgear is published in BS 6626. 

In some cases, the maintenance has to be done at particular times. Continuous process plants are an example. They are run for prolonged periods and then shut down only at predetermined intervals for maintenance and modification/upgrade purposes. Electrical components, vital to the operation of the plant, usually merit inspection on each such occasions and any parts, subject to wear deterioration, should be replaced prematurely to insure against failure operation. Brushes, contactor contacts and the oil of oil-immersed switchgear and control gear, are examples. 

For most items, the maintenance engineer should have little difficulty listing the work to be done when the item is inspected. Among the literature available, BS 6423 and BS 6626 give excellent advice on LV and switchgear and control gear maintenance. For the more complex apparatus the makers instructions should be obtained and followed. The aforementioned HSE and lEE guidance is also helpful. 

British Standard BS 6423 1983 - Code of Practice for maintenance of switchgear and control gear up to 1 kV... 

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