Substation Network Research Articles

PJM Interconnection: model of a smooth operator [electric utility experience

During the summer of 1999, searing heat waves across the United States set air conditioners roaring and brownouts rolling through the grid-that network of substations, transformers, cables and towers that conducts the flow of electricity from supply center to demand point. Here, the author describes how, while local utilities faced outages at the distribution level in the mid-Atlantic states, grid operator PJM Interconnection LLC, of Norristown, Pa., kept its transmission network humming, though not without some difficulty and what the company calls "learning experiences".

Simulation of transformer PD pulse propagation and monitoring for a 500 kV substation

This paper discusses the development of a simulation model to study the propagation of partial discharge (PD) pulses of transformers in a 500 kV substation. The results will be used to design an on-line PD monitoring system for transformers. The impedance matrix of a 500 kV, single-phase transformer is computed based on geometry data and its external coupling network (often referred to as coupling impedance) is calculated with electromagnetic transients program (EMTP). It was found that the frequency characteristic of the coupling network is complex and that the traditional lumped coupling capacitance representation is only feasible at <60 kHz. The entire substation network was included to calculate the PD propagation of the transformer. PD responses are obtained at the tank grounding and 500 kV bushing tap grounding with a simulated PD pulse injected at the 500 kV terminal and 220 kV terminal of the transformer, respectively. Simulation shows that, using the resonant frequency of the substation network as monitoring frequency, one effectively can increase the monitoring sensitivity. The off-line and on-line PD calibration can also be made based on the developed simulation model.

Extended Petri net models for fault diagnosis for substation automation

In previous work Petri net models were developed by the authors (1977) for detecting fault locations in general. In the current paper, the models have been modified to include backup protection as well as primary protection. The modification overcomes many limitations of the original models. Hence, the advanced models are more capable of analysing fault in a highly meshed network or network with more than one layer of protective devices, such as those in substations. The developed methodology is tested using an actual substation network. Fast and accurate results are obtained, and the proposed method has great potential for on-line applications.

Systematized short-circuit analysis of a 2×25 kV electric traction network

Abstract This paper presents a systematic approach for short-circuit analysis of a 2×25 kV electric railway system. This approach uses a full-scale model of a 2×25 kV electric traction network. The model is composed of a substation model, autotransformer (AT) models, and network conductor models. The substation model considers the three most commonly used connection schemes of traction transformers. There are single-phase, V and Scott connections. The AT model considers the impedance and inherent characteristics of the AT, while the network conductor model considers the self and mutual impedances of three major conductors in a traction network (overhead contact wire, return feeder and rail). These models are all in coupling-free type. Therefore they can be easily implemented into a self-developing program or commercial packages, such as a short-circuit program in phase coordinates, the Electromagnetic Transients Program (EMTP), or the Personal Computer Simulation Program with Integrated-Circuit Emphasis (PSPICE). With the proposed models, a short-circuit analysis program is developed by the node admittance matrix method. In this manner, the fault currents in each branch in a traction network as well as the curves of fault currents versus fault location can be easily achieved. Furthermore, the voltages at the overhead contact wire and return feeder along a railway route can be calculated if required.

Planning substation capacity under the single-contingency scenario

Florida Power and Light (FPL) adopts the single contingency emergency policy for its planning of substation capacity. This paper provides an approach to determine the maximum load which a substation can take on under such a policy. The authors' approach consists of two linear programming models which determine: (1) the maximum substation load capacity; and (2) the reallocation of load when a substation's demand cannot be met. Both models are formulated under the single-contingency scenario, an issue which has received little attention in the literature. Not only does this explicit treatment of the scenario provide an exact measure of a substation's load limit, it also raises several important issues which previous works omit. These two models have been applied to the substation network of the Fort Myers District of the State of Florida, USA. >

An economical distribution system for high-density commercial and industrial loads

Central business districts (CBDs) of most major cities of the world are supplied by underground medium-voltage radial feeders or networks which are meshed at medium or low voltage. Radial feeders are the simplest and cheapest way of supplying these major commercial loads, but a feeder fault will affect every customer on that feeder. Mesh networks provide a much more reliable and flexible supply, but require large numbers of medium-voltage (MV) or low-voltage (LV) circuit breakers such as network protectors for ease of operation. Using the CBD of South East Queensland, Australia as an example the authors present a more economical network of distribution substations. By minimising the number of circuit breakers and adopting standardised modules leading to standard layout, circuitry and protection designs, it has been possible to significantly reduce the cost of distribution.

On the Validation and Analysis of a New Method for Power Network Connecticity Determination

The analysis method and results of a power network connectivity determination algorithm, part of the CONCE project, the central part of ENHER's computerized dispatching system, are reported together with a validation of the latter through practical measurements. The algorithm is constructed by repeated invocation of the same connectivity determination procedure for an abstract graph. Although emphasis is given to a version consisting of two steps, substation and overall network, a three step imiplementation is also suggested together with its possible advantages. The main concepts upon which the algorithm is based are reviewed briefly. The analysis shows that the processor time involved in its execution is linearly proportional to the power network dimensions. This fact suggests that the algorithm could be used with advantage for large power networks.