The first no-load phasor test of secondary equipment of UHV converter station in the country was completed
On October 20, the country’s first no-load phasor test of the secondary equipment of the UHV converter station was completed.
“The three-phase current of the 75A3 circuit breaker is in correct phase compared with the reference voltage, and the primary and secondary polarity connections of the on-site current transformer are correct…” As the report from maintenance employee Zhao Xiangdong came, Ningxia Electric Power Ultra-High Voltage Company successfully completed the ±800,000 Adjustment of 750 kV current transformer ratio and no-load phasor testing at Fulingzhou Converter Station.
So what is so innovative about this work?
First, let’s understand what phasor testing is
The phasor test is actually to verify the transformation ratio of the secondary current loop and measure the polarity (positive pole, reverse pole).
Traditional guard phasor testing
The actual load voltage, current size and angle must be measured when the equipment is powered on to determine the correctness of the circuit. However, the equipment needs to carry out a large number of switching operations from power outage to power transmission, which is time-consuming, labor-intensive and risky.
No load phasor test
There is no need to send power to the equipment. During the power outage of the equipment, the tester can be used in advance to simulate the voltage and current of the actual live operation of the equipment, and then the voltage, current size and angle in the loop can be measured with special instruments to verify the polarity of the secondary wiring of the current transformer. Check whether the polarity is correct, avoid the risk of grid tripping caused by incorrect polarity in advance, and ensure the safe operation of the equipment. Therefore, compared with traditional testing when the equipment is powered on, it has the advantages of high safety, fast operation, and the ability to avoid risks in advance.
For the first time in the country, what safety benefits has it brought?
In order to improve the transmission capacity of the ±800 kV Lingshao UHV DC transmission project (Ningxia Lingzhou Converter Station – Zhejiang Shaoxing Converter Station), Ningxia Electric Power Ultra High Voltage Company has carried out the Ninth and Section 750 kV Lingzhou Converter Station The current transformer ratios of the six circuit breakers in the ten series were adjusted. According to safety requirements, the polarity of the relevant current transformer must be tested after adjustment to ensure that the current direction collected by the relay protection equipment is correct and to prevent the relay protection equipment from malfunctioning and causing the equipment to trip without failure.
“We took advantage of the Lingshao DC power outage maintenance opportunity and used unloaded phasor measurement technology for the first time to carry out protection phasor testing. This new test reduced more than 30 switching operations, reducing the safety risks of personnel switching operations and avoiding It eliminates the power grid risk caused by the shutdown of the 750 kV busbar and effectively improves the reliability of power grid operation.” Zhao Xiangdong said. This work effectively solved the problems existing in traditional phasor testing, such as multiple cooperation professionals, large switching operations, and high grid security risks, and provided typical experience for the development of similar types of work on power grid equipment.