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This paper investigates a number of design, operation and lifetime management experiences of feeder unit protection systems installed on National Grid Electricity Transmission (NGET) UK networks. The paper will consider the policy, application design and operational experiences under the following categories in particular since the move to numeric protection: Policy and application design SDH communication...
This paper investigates how an on-load tap changer (OLTC) can be used to regulate the unbalanced three-phase voltages when single phase unbalanced loads are connected to a radial LV distribution feeder. An overview of current voltage regulation technologies for distribution network is presented. Two voltage regulation strategies are developed to eliminate the effect of the unbalanced single phase...
This paper investigates a number of design, operation and lifetime management experiences of transformer protection systems installed on National Grid Electricity Transmission (NGET) networks. The paper will consider the policy, application design and operational experiences under the following categories particularly since the move to numeric protection: Policy and application design Operational...
Traction transformer is often on short-time overload state to meet the needs of traction load. In order to prevent the damage to the traction transformer caused by overthermal which is produced by load current, inverse time overcurrent protection is often used in China. Firstly, this paper introduces inverse time overcurrent protection and three standard characteristic equations of inverse time overcurrent...
Pantograph of an en-energized train may never run through n neutral section. As it does so, the arc generated across the pantograph will likely short the two feeding lines together at both sides of the neutral section where two phases are separated, The fault is called out-of-phase short-circuit fault for which short two out-of-phase feeding lines. Traditional feeder distance protection and current...
Historically, the distribution network has been planned in order to operate in radial configuration. Protective relays are adopted to detect system abnormalities and to execute appropriate commands to isolate swiftly only the faulty component from the healthy system. Nowadays, the regulation schemes implemented by Regulators require that Distribution Companies reduce number and duration of supply...
Progress in the development of communication network technology continues apace and Ethernet technology, once limited to local area network applications, is increasingly being considered for use as the backbone technology for wide area communication networks. The technology, most commonly referred to as “Carrier Ethernet”, seems likely to become the dominant technology within wide area networks ultimately...
Although there has been a practice of transposition of transmission lines, most of the real life EHV/UHV lines are untransposed. The distance protection of such lines becomes very complicated. With the advent of Global Positioning System (GPS) and Fiber optics technology, current differential protection can be a better choice for such lines. This paper proposes current differential protection scheme...
There were many accidents of large-scale wind turbines disconnecting from power grid in 2011. Single-phase-to-ground fault cannot be correctly detected. Single-phase-to-ground evolved to phase-to-phase fault. Phase-to-phase fault was isolated slowly, which led to low voltage. And wind turbines without enough low voltage ride-through capacity disconnected from the grid. After some wind turbines disconnected...
A large-scale implementation of distributed generation (DG) for households involves each house generating its energy from photovoltaic (PV) cells. This approach is particularly suitable in rural electrification projects where demand is relatively low and yet grid connection is costly. A meshed microgrid is an attractive solution for energy generation and sharing in domestic electrification projects...
The standard IEC 61850 contributes the manufacturers and the end users. But it also makes many obstacles to the modification of the conventional substation. This paper presents a scheme which modifies an in-service conventional substation gradually to a modern substation which conforms to IEC 61850 standards. The procedure of the modification is divided into three stages. During the first stage, all...
Busbar protection is described for a bus with current inputs for up to 32 bays. For busbar protection with IEDs and MUs using IEC61850–9–2 process bus, communication traffic jams are the main concern, due to transferring 80 samples/cycle data from all bay MUs to IED via 100BASE-FX. This paper describes peer-to-peer connection between MUs and IED in order to segrigate the SV messages of 32 bays on...
The project to install new cables in the Woodhead Tunnel forming part of National Grid's (NGET) 400kV transmission system running across the Pennines, requires a state of the art cable monitoring and protection system. The availability of IEC61850 offers the opportunity to provide a simple but effective system in an early long haul application.
The large AC generators in a power plant are core facilities for providing stable production and supply of electric power in many applications. The generator protection system has very important role in maintaining stability in a power system. The generator protection systems in South Korea have been imported and operated through a turn-key from overseas entirely. Recently, with increase in the power...
Autoreclosure provides a means of improving power transmitting ability and system stability. The conventional reclosure adopts the fixed dead time interval strategy, that is, the reclosure is activated after a time delay to restore the system to normal as quickly as possible without regard to the system conditions; however, these simple techniques cannot give the optimal operating performance. For...
The new generation of current sensors, such as Rogowski coils, have performance characteristics that can improve design and operation of modern power systems. This paper presents novel solutions that integrate protection, control, and metering functions for power transformers and cables by sharing signals from the same Rogowski coils.
The paper describes a Transient Bias technique designed to overcome the effects of Current Transformer (CT) saturation, which might severely affect the behaviour of a protection system. This Transient Biasing, as the name implies, is only active during transient conditions in the power system, and it decays quickly once the transients disappear. A complementary algorithm for fast detection of external...
The quest for intelligent, so called Smart Grid technology is seen by many as the key to future exploitation of renewable energy sources and the inclusion on the Grid of home grown generation from micro CHP systems. But, as Keith Hamilton, Group Managing Director of PBSI Group Limited explains, the prerequisite for the establishment of Smart Grids relies on a significant investment in equipment as...
When applied over asymmetrical or potentially asymmetrical channels (unequal channel propagation times in the transmitting and receiving directions), such as commercial-class SDH/SONET networks, line current differential schemes need an external time reference for current data alignment if the sensitivity of the differential scheme is to be preserved. Modern line differential schemes can handle a...
Accurate fault location on transmission lines becomes increasingly beneficial by reducing outage times and allowing faster restoration of scarce power system assets back into service. Having natural access to synchronized remote current data, line current differential protection schemes can incorporate multiterminal fault location algorithms, allowing for more accurate fault location compared with...
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