Testing Electrical Substations

Summary

This video explains the key components of energy systems, focusing on power plants and substations. It highlights the importance of transformers, protection and control systems, and switching elements like circuit breakers. The video emphasizes the need for proper testing during commissioning, maintenance, and refurbishment to ensure the seamless interaction of components. Specific tests for current transformers (CTs) and voltage transformers (VTs) are discussed, including checking accuracy, phase displacement, and resistance. The video also stresses the critical role of ensuring proper interaction between all components for reliable energy supply.

Takeaways

• ⚡ Power plants and substations are key components of the energy system, requiring seamless interaction between individual parts for reliable electricity supply.
• 🔧 Commissioning tests ensure manufacturing data verification, identify possible transportation damage, and confirm correct wiring for system setup.
• ♻️ In refurbishment projects, parts with shorter lifespans are renewed, while others remain in service, requiring performance verification of remaining components.
• 🔌 Current Transformers (CTs) transform primary current to secondary current needed for control, protection, and metering systems with accuracy in amplitude, polarity, and phase.
• 🛡️ Protection CTs must handle high fault currents without saturation, while metering CTs must provide accurate readings and protect energy meters by saturating slightly above operational range.
• ⚙️ CT testing includes ratio and phase displacement verification, polarity testing, magnetization curve measurement, and winding resistance checks, ensuring proper function.
• ⚡ Voltage Transformers (VTs) transform primary voltages into manageable levels for control and metering systems, with testing focused on ratio, polarity, and burden checks.
• 🔩 Circuit breakers and disconnectors require good contact connections, measured through contact resistance tests to prevent energy losses and ensure operational integrity.
• 🖇️ Proper wiring between CTs, VTs, and protection/control systems is crucial for correct interaction, requiring thorough verification after component testing.
• ✅ Injecting fault-level currents into the CT's primary side is necessary to verify the entire protection chain, ensuring the substation or power plant functions correctly.

Q & A

What are the major components of an energy system as mentioned in the script?

The major components of an energy system include power plants, substations, power transformers, instrument transformers, protection and control systems, and switching elements like circuit breakers and disconnectors.

What is the purpose of commissioning tests in power plants or substations?

Commissioning tests are performed to verify manufacturing data, identify and fix possible transportation damages, and confirm correct wiring to ensure the correct operation of all components and their interaction throughout the lifecycle of the plant.

What is involved in refurbishment projects for substations?

In refurbishment projects, parts of the system with a shorter lifespan are renewed, while other components remain in service. The performance of the remaining apparatus must be verified, and the interaction between old and new components must be confirmed.

What kind of maintenance activities are carried out during the operational lifetime of a substation?

During a substation’s operational lifetime, measurements are performed as part of periodic maintenance activities or for troubleshooting. These tests ensure the continued functionality and accuracy of components.

What are the key functions of current transformers (CTs) in a power system?

Current transformers (CTs) transform primary current into secondary current needed for control, protection, and metering systems. They must provide accurate amplitude, polarity, and phase to ensure proper operation of protection systems and accurate metering.

Why is it important for protection CTs to avoid saturation?

Protection CTs must avoid saturation when driving high fault currents to the protection system because saturation would prevent the CT from operating properly, which could affect the reliability of the protection system.

How are metering CTs designed to protect energy meters?

Metering CTs are designed to provide accuracy within operational current ranges and to saturate slightly above this range to protect energy meters from excessive currents.

What are the key tests conducted on voltage transformers (VTs) during commissioning?

During commissioning or refurbishment, VTs are tested for ratio and polarity, and their burden is measured to ensure they transform primary voltages accurately for control, protection, and metering systems.

What is the purpose of contact resistance measurements in substation components?

Contact resistance measurements ensure that connections within components like circuit breakers and disconnectors have tight contacts, minimizing operational losses and identifying issues like corrosion.

How is the interaction of various components in a substation verified after individual tests?

After testing individual components, their interactions are verified by injecting current on the CT’s primary side, simulating fault conditions, and ensuring that the entire chain, including protection relays and circuit breakers, operates correctly.