Power control centres

Figure 13.1 A typical cubicle-type power control centre (Courtesy ECS)...

These assemblies are fitted with switching devices (breakers, switches, fuse switches and contactors etc.) and control and measuring instruments, indicating, regtilating and protective devices etc. to transform the assemblies into composite units, called control centres to perform a number of functions in the field of distribution and control of electrical power. Some of these functions may be one or more of the following ... 

These may receive power from one or more sources of supplies and distribute them to different load centres, which may be a motor control centre (MCC) or a distribution board (DB), as illustrated in Figures 13.2... 

When there is only one process line and one MCC alone is adequate to control the entire process, it is possible to combine the PCC and the MCC into one unit to save on space and cost. The assembly may now be called a PMCC (power-cum-motor control centre). 

Recommended practices for seismic gualitlcation of class IE equipment for nuclear power generating stations (NPGS) For qualifying class IE motor control centres for nuclear power generating stations (NPGS)... 

A good rule-of-thumb guide is to assume that between 15% and 25% extra capacity will be required. Hence the chosen rating will be 115% to 125% of the best-known estimate at the early design stage. This requirement also applies to power transformers and their main cables or overhead power lines, and to outgoing feeder cables to auxiliary switchboards and motor control centres. It does not usually apply to individual motor consumers, see Chapter 1. 

This method is commonly used in the oil industry because of the predominance of steelwork in a typical installation. In this method the power system is earthed separately from the equipment frames and cnbicles. The star point at the sonrce is the only common earthing point. The lEG standard reqnires the circuit to be protected by a residual earth fault current device at the switchboard or motor control centre, where the consumer is located in a Zone 1 area. 

The system receives its main power from a circuit breaker (6) or contactor in the upstream switchboard or motor control centre. This switchgear will contain the main power protective relays... 

It may not be necessary to put all the high-voltage consumers in the priority table. The most economical approach is to select enough consumers such that their total nameplate power, when multiphed by a factor (K), is equal to the rated output of one generator when it is operating at its highest ambient temperature in its dirty state . In Table 16.3 this would apply to the group of items numbered approximately 16 to 23, such that the motor control centres are not included. The factor K will therefore need to take account of ... 

Somewhere in the specification, or the data sheet, should be stated the expected life duration of the eqnipment, e.g. 25 years, and a reasonable duration of continuous service between major maintenance operations, e.g. 3, 4 or 5 years. These durations will depend upon the type of equipment, but for major items such as large generators, large high-voltage motors, switchboards, motor control centres, power transformers, these durations can be regarded as typical for the oil industry. 

The AMDR is equipped with some instruments that are used to detect the surrounding environment and transfer information back to the control centre. The explosion risk is very high when these instruments and equipments in service. So, we should use the intrinsically safe electrical equipment or other special design for the electrical equipment. In principle, the flame-proof equipment is not allowed to use in mine. But the intrinsically safe electrical equipment is very rarely at present, especially the power supply, motor and other key equipments. Therefore, the AMDR adopted the safety strategy of flame-proof after the redundant safety measures drawn up in the case of the basic principles of electric explosion-proof allowed. 

A cost reduction (up to a factor of 1.5 against the first-of-kind plant) may be achieved in the case of a serial production of the ELENA-NTEP plants. The reactor operates at nominal power in an unattended mode that does not require the involvement of operating personnel in the process control. The start-up, shutdown, routine inspection and if required, repair, are performed by personnel from the control centre on a shift basis. The site security may require auxiliary personnel residing in the plant deployment area. 

Step 3 In reviewing critical equipment and resources consider all necessary measures to manage the incident, ie drainage, firewater management, power supply, control centres, communications etc. Consider the requirements to deal with the more likely scenarios, not just the high impact-low probability events. Assess what the likely level of damage would be to vulnerable equipment and resources, in terms of Table f 9 ... 

Each bay is responsible for (dis)connecting one element from the transmission network. This is achieved by a set of elements - relays and electronic devices of the following two types - either a protection device or a control device. The function of the protection devices is to disconnect the power elements from the transmission network, e.g. as a result of overloading of a line or of a generator. The control devices, on the other hand, are used to connect or disconnect the power elements from the network and are typically used by either the operators in the respective control centres or by special purpose software (SPS) designed to undertake some of the operators functions automatically. 

The on-site provision of a Main Control Room and an Operational Support Centre is consistent with current UK practice in which the Central Control Room is the location of the first control centre to be set up in an emergency. Each UK nuclear power station has a purpose built on-site Emergency Control Centre from which an emergency is managed. 

Sequential instruments. The diagram of the light path of the Thermo Electron-200 ICP spectrometer is shown in Fig. 20.14. The plasma is located in the upper centre of the instrument just above the nebuliser, which is powered by a computer-controlled peristaltic pump. Communication with the instrument takes place on a video display, which not only guides the operator through the use of the system, but also provides graphics to simplify methods development. 

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