AC supply system harmonic impedance measurements are discussed. On the basis of a given and known switchable shunt impedance and/or nonlinear load and site measurements, three methods are presented. The first approach assumes a no-load distorted busbar and uses basic circuit theory to calculate the required harmonic impedance. The second method disregards any previous busbar distortion and the harmonic injection but it takes into account any busbar distortion prior to the nonlinear load connection. Using a laboratory model and by comparing harmonic impedance results it is shown that both no-load busbar distortions and the correct measurement of harmonic phase angles may strongly affect the accuracy of calculation. >

Practical approaches for AC system harmonic impedance measurements

A digital simulator that permits the integration of an AC transient stability program with a detailed simulation of a DC system is discussed. It provides a means of overcoming limitations of AC studies for which discontinuous and distorted interactions with DC networks are not accurately predicted. The response of the DC network takes into account the dynamics of a large system without the compromises of severe network reduction. A departure from previous practice extends the locations for interfacing the simulations away from the converter buses, and multiple interfaces are accommodated. The interfacing methods and scheduling are described. A simple test example is provided. >

A new approach to dynamic analysis of AC networks incorporating detailed modeling of DC systems. I. Principles and implementation

A technique for laboratory characterization of instrument transformers designed for transmission level voltage and current measurements is presented. The technique is also extended to transient event recorders (TERs). The objective of the method is to determine the suitability of existing substation instrument transformers for harmonic measurements, particularly in the frequency range of 60 to 1500 Hz covering the first 25 harmonics. Specifically, the following characteristics are of interest: transfer function magnitude and phase, linearity, and sensitivity of the frequency response to burdens. The measurement technique is based on exciting the instrument transformer primary with an impulsive waveform. Both input and output waveforms are recorded using laboratory grade probes and digitizers. Digital signal processing techniques are used to compute the instrument transformer frequency response. Several voltage transformers and current transformers in the 230 kV-765 kV voltage range were tested. The results are described. >

Transmission level instrument transformers and transient event recorders characterization for harmonic measurements

In electromagnetic transients studies, only a limited part of a transmission system can be modelled in detail. The remaining parts of the system have to be reduced to equivalents. Simple equivalents which reproduce the network's response at few frequency points can introduce significant errors into the calculated transients. A method to generate network equivalents from the frequency response of its admittance has been developed. The equivalents are in the form of lumped parameter circuits, have a simple structure and reproduce the network's behaviour over a wide frequency range. The developed method was used to generate an equivalent for a sample system. Voltage transients due to an energization of a transmission line from that sample system were calculated. The results of calculations with the full system representation and the developed equivalent showed a good agreement.

Transmission Network Equivalents for Electromagnetic Transients Studies

Considerations on hosting capacity for harmonic distortions on transmission and distribution systems

This paper is Part I of a two part series. The two papers will report part of the research project RP-1138 sponsored by EPRI and BPA on HVDC-AC System Interaction from AC Harmonics. The two papers deal with the harmonic impedance measurement of Bonneville Power Administration's (BPA) system as seen from the Celilo HVDC substation, the development of analytical techniques to calculate the harinonic impedance of the system, and comparison of the calculated and measured results.

HVDC-AC Harmonic Interaction Part I - Development of a Harmonic Measurement System Hardware and Software

This paper is Part II of a two part series. The two papers will report part of the research project RP-1138 sponsored by EPRI and BPA on HVDC-AC System Interaction from AC Harmonics. The two papers describe the harmonic impedance measurement of Bonneville Power Administration's (BPA) system as seen from the Celilo HVDC substation, the development of analytical techniques to calculate the harmonic impedance of the system, and comparison of the calculated and measured results.

HVDC-AC Harmonic Interaction Part II -AC System Harmonic Model with Comparison of Calculated and Measured Data

This paper discusses models of equipment in a HVDC station for the calculation of noise in the carrier frequency range. Comparisons are made between measured and calculated results for individual equipments. Comparison between measured and calculated values of overall station performance is discussed.

Modeling of the DC Converter Equipment in the Carrier Band

As part of a program to develop better tools for predicting noise levels from DC converters, a series of measurements were made of the noise levels produced by the Arrowhead converter of the Square Butte project. In this paper both measurement techniques and measurement results are presented. Voltages were measured on both the ac and the dc systems and on both the line and valve sides of the smoothing reactor and converter transformers. Valve side measurements were made possible by a divider that uses a bushing as the high voltage element. Operation of a noise meter is discussed and a circuit shown that allows quasi-peak levels to be measured with an instrument that normally does not provide a quasi-peak function. Quasi-peak levels are shown to be 7-12 dB higher than average levels. Effects of meter bandwidth are discussed. Internal resonances in the smoothing reactor are shown to be the cause of pronounced peaks and valleys noted on line side measurements. The data suggests that a simple 1/f curve of appropriate magnitude may be a sufficient model of the frequency dependent noise produced by the valves.

C. B. Lindh

Papers

HVDC-AC Harmonic Interaction Part I - Development of a Harmonic Measurement System Hardware and Software

HVDC-AC Harmonic Interaction Part II -AC System Harmonic Model with Comparison of Calculated and Measured Data

Modeling of the DC Converter Equipment in the Carrier Band

Measurements of the Electrical Niose Produced in the Carrier Band by a DC Converter

HVDC-AC system interaction from AC harmonics. Volume 1: Harmonic impedance calculations