Study on Method for Field Secondary Signal Simulation of Optical Current Transformer

Abstract

The optical current transformer play an important role on the security and stability of the power system especially HVDC. The HVDC control and protection system cannot be field verified without field simulation for the optical current transformer secondary signal. But the existing method for field simulation of optical current transformer is lacking for easy to implement and meeting requirement. This paper proposed a novel method for field secondary signal simulation of optical current transformer. The advantage of the method are that not need to explain the photoelectric conversion protocol, easy to implement and meeting requirement, low security risk, and low cost. The field test device has been developed with secondary signal simulation quantity of optical current transformer. Its validity was verified by field testing of secondary signal simulation of optical current transformer in echeng convert station of jiang-cheng ±500kV HVDC transmission project. Introduction The optical current transformer[1,2] is widely used in the power system, especially the HVDC project[3,4], and plays an important role on the security and stability of the power system. As a core measuring equipment of HVDC, the optical current transformer is used to measure current including DC line current, pole bus current, valve high-side current, high-side current and imbalance current between the capacitor of AC or DC filter [5] and provide accurate and reliable measurement data for DC control and protection system[6]. It could have significant impact on performance of the DC control and protection system[7]. The HVDC control and protection system[8] cannot be field verified without field simulation for the optical current transformer secondary signal. The measuring principle and transmission mode of the optical current transformer in HVDC are different with electromagnetic current transformer in AC power system[9,10]. The photoelectric conversion protocol of the optical current transformer which is used to transmit data even is proprietary protocol. The existing method for field simulation of optical current transformer is lacking for easy to implement and meeting requirement. Therefore, the field test for DC control and protection system of HVDC has not been carried out after put into operation. These HVDC projects even have put into operation more than ten years. That is serious problem for security and stability of the power grid. This paper proposed a novel method for field secondary signal simulation of optical current transformer. The advantage of the method are that not need to explain the photoelectric conversion protocol, easy to implement and meeting requirement, low security risk, and low cost. This paper is organized as follows. Section 2 describes the principle of optical current transformer and introduces the existing method for field simulation of optical current transformer. The method for field secondary signal simulation of optical current transformer is proposed in Section 3. According to the proposed method, the field test device has been developed with secondary signal simulation ability of optical current transformer, as shown in section 4. Subsequently, in section 5, the field testing of secondary signal simulation of optical current transformer has been carried out in Echeng 2nd International Conference on Electrical and Electronic Engineering (EEE 2019) Copyright © 2019, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering Research, volume 185