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What is a Control and relay Panel ?
A control and relay Panel is an operation and monitoring equipment which is generally placed in a control room which is at some distance from the Switchyard. We also have panels which has equipment like-Circuit breaker, CT, PT installed inside the panel. All remote operations like closing and opening of isolators, circuit breakers & earth switches are done from this panel. Voltmeter, Ammeter ,MW,MVAR meter, energy meter, all kinds of relays etc are placed on front side of the panel to monitor various parameters. Hooters or Buzzers for different alarms are also placed in this panel to inform and alert operators about abnormalities.
Why do we need Control and relay Panel in the first place?
All electrical equipment can be operated locally from the switchyard- circuit breakers, Isolators ,earth switches can be closed and opened manually from the switchyard itself. We operate them from the remote i.e from Control room due to several reasons:
(Click here to understand how circuit breakers are operated from remote )
(i) Arc production on separation of contacts: All high voltage electrical contacts doesn’t suddenly become potential free as soon as the power is turned off . When the HV contacts open ,there is sparking as the current may still try to maintain its path through the air gap between the contacts. Therefore it may be risky for operators to open the circuits by being Physically present there.
(ii) Faulty isolators and earth switches alignment : When alignment of isolators and earth switches are accurate ,all three phases will open and close together, however the alignment may not be appropriate at all times and this may cause heavy sparking in the phases which is not properly aligned and doesn’t close or open simultaneously with other phases.
(iii) Equipment failure: Any equipment like L.A,C.T,C.V.T ,Bushings of transformer may blast in the switchyard due to various reasons like insulation failure, C.Ts getting open circuited, flashover of insulators due to dust and dirt & other reasons .At present the insulating material used in most of the equipment is made up of Porcelain which can pose serious life risk in case of bursting.
Use of polymer type insulation is one the rise due to this reason ,but detecting a hair crack or puncture may be difficult in case of polymer insulators . Transformer oil which is used in CVT,PT, bushings for insulation and cooling purpose may get very hot and may leak and splash from the equipment during bursting which can be very dangerous.
All above hazards can be easily mitigated by operating these switchyard equipment from a control room using a control panel. Mostly control panel and relay panel up to 132kv voltage level is combined in one panel itself and in 220kv and higher voltage level relay panel may be separate from the control panel. A Relay panel has all kinds of protective relays placed over them.
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Testing and commissioning of control and relay Panel:
During pre-commissioning of panels , following five important tests are conducted :
(i) All switchyard equipment should operate from the panel. All Trip and close switch should operate properly.
(ii) All meters-Voltmeter, MW.MVAR meter etc should be functional. We can check this by giving current through test lamp (single pahase,100/ 200w bulb) in C.T junction box. Three phase voltage can be also injected in P.T/C.V.T for getting three phase voltage in the Panel .
(iii) Buzzers should operate when there is fault or other abnormalities. Panels also have a display which glows and indicate which fault has occurred, this display is called annunciation panel which has many rectangular blocks to indicate different faults or abnormalities. These displays should work in accordance of nature of fault given and abnormalities created manually during testing.
(iv) Energy meter installed in panel should be functional. Its functionality can also be checked by injecting current in metering core of C.T and giving P.T supply from a test kit.
(v) Indication lamps which displays open/close status of switchyard equipment should display equipment status accurately .
After completion of all above mentioned checks and getting satisfactory results , we can then commission a panel and take it into service.
FAQs:
- What is a Control and Relay Panel (CRP)?
A Control and Relay Panel is an essential component in electrical substations and power systems. It houses control devices and protection relays used to monitor, control, and protect the electrical network. - What is the primary purpose of a CRP?
The main purpose of a CRP is to house and provide control and protection for the electrical equipment within a substation. It helps ensure the safe and reliable operation of the power system. - What components are typically found in a Control and Relay Panel?
A CRP typically includes protection relays, control switches, communication equipment, indicating and metering instruments, and various control and monitoring devices. - What are protection relays, and why are they important in a CRP?
Protection relays are devices that detect abnormal operating conditions in the power system and initiate protective actions, such as tripping circuit breakers to isolate faults. They play a critical role in preventing equipment damage and maintaining system stability. - How do control switches and devices in a CRP function?
Control switches and devices allow operators to manually control the substation equipment. These devices include push buttons, selector switches, and disconnect switches that are used for operations like circuit breaker control, isolation, and switching. - What types of protection are typically provided by relays in a CRP?
Relays in a CRP offer various types of protection, including overcurrent protection, distance protection, differential protection, under-voltage protection, and many others, depending on the specific requirements of the power system. - Are CRPs used in both medium-voltage and high-voltage substations?
Yes, CRPs are used in both medium-voltage and high-voltage substations to provide protection and control for various types of electrical equipment, such as transformers, circuit breakers, and busbars. - How is communication integrated into a CRP?
Communication equipment within a CRP enables data exchange between the substation and the central control center. This allows operators to monitor and control the substation remotely and receive status information in real-time. - What is the significance of metering instruments in a CRP?
Metering instruments in a CRP provide information about electrical parameters like voltage, current, power, and energy consumption. This data is essential for monitoring the performance and efficiency of the power system. - Can a CRP be remotely operated?
Yes, many modern CRPs are designed to be remotely operated through supervisory control and data acquisition (SCADA) systems. This remote operation enhances the flexibility and efficiency of power system control. - How is a CRP powered and maintained?
CRPs are typically powered from the substation’s auxiliary power supply, and routine maintenance involves checking the functionality of relays, control devices, and communication equipment. Regular testing and calibration are essential to ensure reliability. Both DC and AC power is used in CRP for various purposes. - What are the safety precautions when working with a CRP?
Safety precautions include following established protocols, wearing appropriate personal protective equipment, and ensuring proper isolation and grounding when working on or around CRPs. - Can a CRP provide fault location information?
Yes, some advanced CRPs are equipped with fault location capabilities, which can help identify the location of electrical faults within the power system, aiding in faster fault resolution. Distance relay is installed in CRP itself which tells about fault location. - Are there standards and regulations governing the design and operation of CRPs?
Yes, there are national and international standards and regulations, such as IEEE and IEC standards, that provide guidelines for the design, testing, and operation of CRPs to ensure their reliability and safety.
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