CPWD has established guidelines for the design and construction of substations in accordance with relevant standards and regulations. These guidelines cover various aspects such as the location and layout of the substation, the electrical equipment and systems to be installed, and the safety measures to be taken.
Some key considerations for substation design and construction as per CPWD guidelines include:
Location: Substations should be located in areas that are easily accessible and provide sufficient space for the installation of equipment.
Layout: The layout of the substation should be designed in such a way that it allows for easy and safe operation and maintenance of the equipment.
Electrical Systems: The electrical systems in the substation should be designed to ensure efficient and reliable power distribution while meeting relevant safety standards.
Equipment: The equipment used in the substation should be of high quality and comply with relevant standards and specifications.
Safety Measures: Appropriate safety measures should be taken to ensure the safety of personnel working in and around the substation, including the installation of protective devices and the provision of training for personnel.
Overall, the design and construction of a substation as per CPWD guidelines aim to ensure reliable and safe distribution of electrical power to consumers.
Equipment's of Sub Station
A substation is an electrical facility used for transforming voltage levels and distributing electrical power to various consumers. It typically contains various electrical equipment that allows for the efficient and reliable distribution of electrical power. Some of the key equipment found in a substation include:
- Transformers: Transformers are used in a substation to convert the voltage level of electrical power from one level to another. This allows for the efficient transmission and distribution of power over long distances.
- Switchgear: Switchgear is a term used to describe a range of equipment used to control, protect, and isolate electrical equipment in a substation. This includes circuit breakers, fuses, isolators, and relays.
- Busbars: Busbars are used to distribute electrical power throughout a substation. They are typically made of copper or aluminum and are designed to carry high levels of electrical current.
- Capacitors: Capacitors are used in a substation to improve the efficiency of the electrical system by reducing the amount of reactive power required. This helps to reduce energy losses and improve the overall reliability of the system.
- Batteries and Chargers: Batteries and chargers are used to provide backup power in case of a power outage. They are typically used to power essential equipment such as control systems, communication equipment, and emergency lighting.
- Instrumentation and Control Systems: These systems are used to monitor and control the electrical equipment in the substation. This includes systems for measuring voltage, current, power, and other parameters.
- Grounding Systems: Grounding systems are used to protect personnel and equipment from electrical faults. This includes grounding rods, grounding grids, and other devices designed to provide a safe path for electrical currents.
- Surge Arresters: Surge arresters are used to protect the electrical equipment from high voltage surges that can damage the equipment. They are typically placed at various points in the electrical system to absorb the energy of the surges and prevent them from damaging the equipment.
- Circuit Switchers: Circuit switchers are used to switch electrical power between different circuits in a substation. They are typically used in conjunction with transformers to control the flow of electrical power.
- Voltage Regulators: Voltage regulators are used to regulate the voltage levels in the electrical system. They are typically used in conjunction with transformers to maintain a constant voltage level despite changes in load.
- Control Panels: Control panels are used to control and monitor the various electrical equipment in the substation. They typically include switches, indicators, and other devices used to control and monitor the electrical system.
- Lightning Protection Systems: Lightning protection systems are used to protect the substation from lightning strikes. This includes lightning rods, grounding systems, and other devices designed to protect the electrical equipment from the effects of lightning.
Overall, the equipment found in a substation is designed to ensure the efficient and reliable distribution of electrical power while meeting relevant safety standards.
1. Transformers:
Transformers are one of the key pieces of equipment found in a substation and are used to convert the voltage level of electrical power from one level to another. As per CPWD guidelines, the design and installation of transformers in a substation must adhere to various standards and specifications to ensure efficient and reliable operation. Some key considerations for transformers as per CPWD guidelines include:
Capacity: The capacity of the transformer should be selected based on the expected load demand and the available power supply. The capacity should also take into account any future expansion plans for the electrical system.
Type: The type of transformer used in the substation should be selected based on the specific requirements of the application. This includes factors such as voltage level, load demand, and efficiency.
Cooling System: The cooling system used in the transformer should be designed to ensure efficient and reliable operation. This includes selecting the appropriate cooling method (such as air or oil) and designing the cooling system to provide sufficient cooling capacity.
Insulation: The transformer should be designed with appropriate insulation to ensure safe and reliable operation. This includes selecting the appropriate insulation material and ensuring that it is installed correctly.
Protection: The transformer should be protected from various electrical faults and overloads. This includes installing protective devices such as fuses, relays, and circuit breakers.
Testing: The transformer should be tested before installation to ensure that it meets the relevant standards and specifications. This includes testing for factors such as insulation resistance, winding resistance, and impedance.
Overall, the design and installation of transformers in a substation as per CPWD guidelines aim to ensure efficient and reliable operation while meeting relevant safety standards. The specific requirements for transformers may vary depending on the size and complexity of the substation, as well as the specific requirements of the application.
Factory & Site Inspection of Transformer
Factory and site inspections are important steps in ensuring the quality and reliability of transformers used in a substation. Both inspections involve a thorough evaluation of the transformer to ensure that it meets the relevant standards and specifications. Here are some of the key considerations for factory and site inspections of transformers:
Factory Inspection:
- Design Review: The design of the transformer is reviewed to ensure that it meets the requirements specified by the client, relevant standards, and regulations.
- Materials Inspection: The quality of the materials used in the transformer is inspected to ensure that they meet the relevant standards and specifications.
- Manufacturing Process: The manufacturing process of the transformer is inspected to ensure that it is carried out in accordance with the relevant standards and specifications.
- Testing: The transformer is tested in the factory to ensure that it meets the specified performance requirements.
Site Inspection:
- Installation: The transformer is inspected to ensure that it is installed correctly in accordance with the relevant standards and specifications.
- Electrical Testing: The transformer is tested to ensure that it is functioning correctly and meeting the specified performance requirements.
- Grounding: The grounding of the transformer is inspected to ensure that it meets the relevant standards and regulations.
- Protection: The protective devices installed in the transformer are inspected to ensure that they are functioning correctly.
Overall, factory and site inspections of transformers are important steps in ensuring the quality and reliability of the transformers used in a substation. These inspections help to ensure that the transformer meets the relevant standards and specifications and is installed correctly, which in turn helps to ensure the safe and efficient operation of the electrical system.
Transformer Test as Per CPWD
Here are some of the tests that may be required as per CPWD:
Routine Test: This test is performed on every transformer to check its performance under normal operating conditions. It includes tests such as measurement of winding resistance, voltage ratio, and impedance voltage.
A. Winding Resistance Test: It is performed on transformers to measure the resistance of the transformer windings. The test involves measuring the resistance of each winding, i.e., primary and secondary, using a low-resistance ohmmeter.
During the winding resistance test, the transformer is disconnected from the power supply, and the resistance of each winding is measured using a low-resistance ohmmeter. The measured resistance is compared to the specified resistance value for the transformer, and if it falls within the acceptable range, the transformer passes the test.
The winding resistance test is important because the resistance of the transformer windings affects the amount of current that can be carried by the transformer without exceeding its temperature limits. If the winding resistance is too high, the transformer will not be able to handle the rated current, and this can cause overheating and damage to the transformer.
B. Voltage Ratio Test: It is performed on transformers to verify the turns ratio of the transformer. The turns ratio of a transformer is the ratio of the number of turns of wire on the primary winding to the number of turns on the secondary winding.
During the voltage ratio test, the transformer is energized with a known voltage on the primary winding and the voltage on the secondary winding is measured. The ratio of the measured secondary voltage to the applied primary voltage is then calculated, and this is compared to the specified turns ratio for the transformer. If the measured ratio is within the specified limits, the transformer passes the voltage ratio test.
This test is important because the voltage ratio is a critical parameter that determines the transformer's output voltage. If the turns ratio is incorrect, the transformer's output voltage will not be the desired value, and this can cause problems in the electrical system.
C. Impedance Voltage Test: The impedance voltage test is a routine test that is performed on transformers to determine the transformer's impedance voltage, which is the voltage drop that occurs in the transformer when a full load current flows through it. The test is also known as the short-circuit impedance test.
During the impedance voltage test, the transformer is short-circuited on the secondary side, and a low voltage is applied on the primary winding. The voltage drop across the primary winding is then measured, and this voltage is called the impedance voltage. The test is performed at the rated frequency and the rated voltage.
The impedance voltage test is important because the transformer's impedance affects the performance of the electrical system. The impedance determines the amount of voltage drop that occurs in the transformer when a load is applied, and this can affect the overall voltage regulation of the electrical system.
All these Test usually performed as part of the routine tests that are carried out on every transformer before it is commissioned for use.
Type Test: This test is performed on a sample transformer of each rating and design to ensure that it meets the required standards and specifications. The test includes all the tests performed during routine tests and additional tests such as insulation resistance, dielectric strength, and temperature rise.
A. Insulation Resistance Test: It is performed on transformers to verify the integrity of the transformer's insulation system. The test involves measuring the resistance of the insulation between the transformer windings and between the windings and ground.
During the insulation resistance test, the transformer is disconnected from the power supply, and a high voltage is applied to the insulation between the windings and ground or between the windings. The insulation resistance is then measured using a high-resistance megohmmeter.
The insulation resistance test is important because it helps to ensure that the transformer's insulation system is free from defects, such as cracks, moisture, or contamination. Defective insulation can cause electrical arcing or breakdown, which can damage the transformer or the electrical system.
B. Dielectric Strength Test: It is performed on electrical equipment, including transformers, to verify their electrical insulation properties. The test involves applying a high voltage to the insulation material of the equipment to determine the voltage at which the insulation breaks down.
During the test, the equipment is connected to a high-voltage source, and the voltage is gradually increased until the insulation breaks down. The voltage at which breakdown occurs is recorded, and this is known as the dielectric strength of the equipment.
The dielectric strength test is important because it helps to ensure that the electrical equipment is adequately insulated to prevent electrical arcing or breakdown. Electrical arcing or breakdown can cause equipment failure, damage to the electrical system, or even injury to personnel.
C. Temperature Rise Test: It is performed on transformers to determine the temperature rise of the transformer under full load conditions. The test involves measuring the temperature of the transformer windings and the transformer oil before and after the transformer is subjected to full load current for a specified period.
During the temperature rise test, the transformer is loaded to its full rated current, and the temperature of the transformer windings and oil is monitored using temperature sensors. The test is typically performed for a period of four to eight hours, depending on the transformer's rating.
The temperature rise test is important because it helps to ensure that the transformer can operate safely and efficiently under full load conditions without overheating. Overheating can cause the transformer's insulation to deteriorate, which can lead to equipment failure or even electrical fires.
All these test is usually performed as part of the Type tests that are carried out on every transformer before it is commissioned for use.
Lightning Impulse Test: This test is performed to determine the ability of the transformer to withstand lightning impulses. The test involves applying a high voltage impulse to the transformer and measuring the response.
Short Circuit Test: This test is performed to determine the impedance and losses of the transformer under short circuit conditions.
Magnetic Balance Test: This test is performed to ensure that the magnetic field in the transformer is balanced.
Transformer Oil Test: This test is performed to check the quality of the transformer oil, including its dielectric strength, moisture content, and acidity.
Sound Level Test: This test is performed to measure the noise level of the transformer during operation and ensure that it is within the required limits.
Overall, these tests help to ensure that the transformer is reliable, efficient, and safe for use in the electrical system. The specific tests performed may vary depending on the transformer's size, type, and the requirements of the relevant standards and specifications.
2. Switchgear:
As per CPWD specifications, switchgear refers to electrical equipment that is used to protect, control, and isolate electrical circuits. The switchgear is used to interrupt and isolate faulty electrical circuits, provide electrical isolation to equipment for maintenance, and control the flow of electrical power.
The switchgear used in building electrical systems as per CPWD specifications includes circuit breakers, isolators, earth leakage protection devices, and other protective devices. The switchgear is designed to operate under normal and abnormal conditions to ensure the safety of the building occupants and the electrical equipment.
The CPWD specifications provide guidelines for the selection, installation, and testing of switchgear in building electrical systems. The switchgear should be selected based on the electrical load and the type of equipment being protected. The installation of the switchgear should be carried out by trained personnel in accordance with the manufacturer's instructions and the relevant standards.
The switchgear should be tested before commissioning to ensure that it meets the specified standards and is operating correctly. The tests include visual inspection, functional testing, and electrical testing, such as insulation resistance testing and high voltage testing. The test results should be recorded and compared to the manufacturer's specifications to ensure that the switchgear meets the required standards.
Switchgear Test as Per CPWD
As per CPWD specifications, switchgear used in building electrical systems should be tested before commissioning to ensure that it meets the specified standards and is operating correctly. The switchgear tests include visual inspection, functional testing, and electrical testing.
A. Visual Inspection: Visual inspection is carried out to ensure that the switchgear is installed correctly and that all components are in good condition. The visual inspection includes checking for any signs of damage, loose connections, or incorrect wiring.
B. Functional Testing: Functional testing is carried out to ensure that the switchgear operates correctly under normal and abnormal conditions. The functional tests include testing the operation of circuit breakers, isolators, earth leakage protection devices, and other protective devices. The tests include verifying the proper operation of the switching and tripping mechanisms, checking the alignment of the contacts, and verifying that the switchgear operates correctly under fault conditions.
C. Electrical Testing: Electrical testing is carried out to verify that the switchgear meets the specified electrical parameters. The electrical tests include insulation resistance testing, contact resistance testing, and high voltage testing. The tests are performed to verify the insulation resistance between the live parts and the ground, to verify the contact resistance of the switchgear contacts, and to verify the ability of the switchgear to withstand high voltage stresses.
Factorty Test as Per CPWD
As per CPWD specifications, switchgear used in building electrical systems should undergo factory testing before shipment to the installation site. The factory testing is carried out to ensure that the switchgear meets the specified standards and is operating correctly.
The factory testing of switchgear includes type tests and routine tests. The type tests are carried out on a sample of the switchgear to verify that it meets the specified parameters, such as the rated voltage, current, and short circuit breaking capacity. The routine tests are carried out on each individual unit of the switchgear to ensure that it meets the same parameters as the sample tested during the type tests.
The factory testing of switchgear includes the following tests:
Insulation Resistance Test: This test is carried out to measure the insulation resistance between the live parts and ground. The test is performed at a specified voltage and temperature.
High Voltage Test: This test is carried out to verify the ability of the switchgear to withstand high voltage stresses. The test is performed at a specified voltage and for a specified duration.
Contact Resistance Test: This test is carried out to verify the contact resistance of the switchgear contacts. The test is performed using a low DC voltage and a calibrated milliohmmeter.
Operation Test: This test is carried out to verify the proper operation of the switching and tripping mechanisms. The test includes verifying the alignment of the contacts, the proper operation of the auxiliary contacts, and the proper operation of the mechanical interlocks.
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