David J. Pileggi

The effect of modern compact fluorescent lights on voltage distortion

The results of a computer simulation of three real life 13.8 kV feeders supplying consumers with nonlinear loads which include CFLs (compact fluorescent lights) with electronic ballasts are presented. The computer simulations are supported by laboratory testing and in-the-home installation/monitoring of CFLs. The results are combined with load research information regarding residential load profiles to produce load models for use in computer simulation of the behavior of three distribution feeders. The input current to electronically ballasted CFLs has unusually high distortion, (THD (total harmonic distortion) >100%). The main conclusion is that for a 15 kV class feeder with a maximum 10 MVA load, the total load of electronically ballasted CFLs should not exceed 100 kW if the voltage THD is to be kept >

Current Harmonics, Voltage Distortion, and Powers Associated with Electric Vehicle Battery Chargers Distributed on the Residential Power System

The harmonic performance of the networks of several types of electric vehicle (EV) battery chargers is documented. Cumulative effects at the substation level for random distributions of each of five different charger types are reported. Chargers with and without current- smoothing inductors and with and without controlled rectifiers for maintenance of constant current are included. Results are reported as magnitudes of expected harmonic current; active power; apparent, reactive, and distortive volt amperes; and power factor hour by hour over typical daily recharge cycles for the network of chargers. Results regarding comparisons among chargers demonstrate the desirability of including a current-smoothing inductor in the charging circuit and indicate that constant-current type chargers using controlled rectifiers generate significantly more harmonic current than the simple noncontrolled taper-current chargers. Typical third harmonic current values of 15 A per charger on the 120-V side and 20 A per phase on the 12.8-kV side for a network of chargers (at ten percent penetration of chargers into the residential distribution network) indicate the possibility for harmful effects to customer and utility equipment and for interference into communications circuits. The results reported here should be useful in both predicting harmful effects at various densities of EV chargers on the residential network and in designing chargers to minimize those effects. supported in part by the New England Electric System.

Voltage distortion in distribution feeders with nonlinear loads

The voltage of three real-life 13.8 kV feeders supplying customers with nonlinear loads was analyzed by means of computer simulations. Three classes of nonlinear loads were considered. Each class is characteristic for different types of AC to DC converters such as the input DC supply used for adjustable-speed-drives, battery chargers, PCs, TVs and electronically ballasted lights. The analysis is based on the determination of the most harmonic susceptible busses and their response to each harmonic frequency. A new expeditive method that takes into account the background harmonic voltage phasor, and an equivalent bus impedance was developed and used to compute the maximum nonlinear loads that yields VTHD=5%, (voltage total harmonic distortion). The main conclusion of this work is that when mitigation methods are not used, for a 15 kV class feeder with a maximum 10 MVA installed load, the total nonlinear residential load should not exceed 300 kW if the ITHD 100%. >

Distribution feeders with nonlinear loads in the northeast USA. I. Voltage distortion forecast

This paper forecasts the level of voltage total harmonic distortion (VTHD) for a typical customer during the next two decades. The study is based on a growth projection of residential, commercial and industrial loads and the acceptance of new technologies such as adjustable speed drives (ASDs) and electronic ballasts. The forecast was generated for the service areas of the above two utilities and applied to three real-life, 13.8 kV feeders. The harmonic power flow was determined for each feeder under the assumption of different levels of current distortions and different types of nonlinear loads. It was found that short feeders, 5 mi. It was found that the rate of increase of VTHD could be as low as 0.01%/year for a short feeder without parallel resonances or could be as high as 0.35%/year in harmonic sensitive systems. >

The engineering economics of power systems harmonics in subdistribution feeders: a preliminary study

A method for the computation of the cost of harmonic losses in a subdistribution feeder is presented. The cost of harmonics, including the cost of the filters, is compared with the cost of the 60 Hz power loss as well as the total annual cost of the system. Evaluating the cost of harmonic current

Distribution feeders with nonlinear loads in the northeast USA. II. Economic evaluation of harmonic effects

/A/year or the incremental cost of the harmonic reactive power,

Evaluation of single-point measurements method for harmonic pollution cost allocation

/kVar/year, is recommended. >

A Non-Contact Technique for Determining Harmonic Currents Present in Individual Conductors of Overhead Lines

For pt.I see ibid., vol.10, no.1, p.340-7 (1995). This paper presents an estimate in present worth values (1990 dollars) of the cost to the electric utility to contend with harmonic pollution. These costs include the total active power loss value as well as the capital invested in the design and construction of filtering stations needed to maintain the voltage distortion below 50%. This study focuses on three different 13.8 kV, 10 MVA class feeders. The results are given in the form of a ratio

Field Experience with Harmonics Injecting Equipment in Distribution Networks

year/kVA harmonic. >

An Automated Noncontact Measurement System for Current Harmonics in Aerial Transmission and Distribution Systems

This paper reports on the reliability of single-point measurements for harmonic pollution cost allocation. Simulated results give the correlation between the cost and four physical electrical quantities that can be measured at the end-user bus: harmonic active power; harmonic apparent power; total harmonic current squared; and nonfundamental apparent power squared. The nonfundamental apparent power squared produced the best correlation between the ideal cost and the single-point simulated measurement, with errors less than 5%.