Study on the Effect of Multi-Type Current Transformers Hybrid Operation on Differential Protection of the Bus Based on Dynamic Simulation

This paper analyzes characteristics of multi type current transformers hybrid operation for each branch of the bus and their effects on differential protection of the bus. By theoretically analyzing transmission characteristics of multi type current transformers and their influence factors, we study the dynamic model testing method of multi type current transformers for the bus, and design 3 kinds of testing schemes by making the equivalent model based on the field of P-level current transformer, TPY-level current transformer and electronic current transformer, and build the hybrid operation testing platform of multi type current transformers. Finally, we compare and analyze the transmission characteristics difference of multi type current transformers on the same branch and the characteristics difference of hybrid operation in two successive external faults, analyze the cause behind the differences, and put forward the corresponding improvement measures.

High-Impedance Bus Differential Protection Modeling in ATP/MODELS

This paper presents a modeling of a high-impedance bus differential protection logic using the ATP (Alternative Transients Program) MODELS language. The model is validated using ATP simulations on an electrical system consisting of a sectionalized bus arrangement with four transmission lines (TLs) and two autotransformers. The obtained results validate the model and present some of the advantages of using this type of bus protection, such as fast and safe operation, even when under adverse conditions such as current transformers (CTs) magnetic core saturation upon the occurrence of external faults.

Complex Percentage Differential Relay

This paper introduces a new complex percentage differential relay for bus protection. It allows greater CT errors during the external fault and is still sensitive to the intemal fault with high fault resistance or out-flowing current.The CTs of the differential circuit of the new relay may have different transformation ratio, so the new relay can share CTs with other relays and don’t need special CTs only for differential protection. It may be applied in transformer differential protection as well.

An adaptive limited wide area differential protection for power grid with microsources

The operation mode of power grids with intermittent distributed generations(DGs)changes frequently due to the bidirectional power flow.In comparison with the conventional grids,the protection relays in power grids with micro-sources are more difficult to set.To tackle this problem,this paper proposes an extended bus differential protection(EBDP)strategy based on the limited wide area(LWA).In this method,the micro-grids are divided into several protection areas at the core of the bus.The whole protection areas are protected by the wide area current differential relays,which are also configured to protect each component in this protection area.Moreover,the protection areas can be changed adaptively according to the power flow direction.Finally,a micro-grid model with multiple DGs is developed using the PSCAD/EMTDC platform.The simulation results indicate that the proposed adaptive limited wide area differential protection(LWADP)has better performance than the traditional relaying protection in detecting the faulty area in micro-grids and isolating the fault,and can be widely utilized in larger micro-grids.