Hioki 3196 Manuale utente

Case Studies of

Power Quality Surveys

using

Model 3196 Power Quality Analyzer

HIOKI E.E. CORPORATION

July 2005

Rev. 5

TABLE OF CONTENTS

Power Quality Basics: Current Power Supply Environment Page 1

Power Quality Standards Page 1

Main Power Quality Parameters Page 2 to 4

Case Study 1: Inrush Current and Current RMS Value of a Dryer Page 5 to 6

Case Study 2:

Switching of Power Factor Improvement

Capacitor

Page 7 to 8

Case Study 3:

Voltage Dip (Instantaneous Voltage Drop

- at Receptacle

Page 9 to 10

Case Study 4:

Voltage Dip (Instantaneous Voltage Drop)

- at Distribution Panel

Page 11

Case Study 5:

Transient Overvoltage

Page 12 to 13

Case Study 6:

Periodical Instantaneous Voltage Drop

Page 14

Case Study 7:

General UPS Switching Waveform

Page 15

Case Study 8: Page 16

Case Study 9: Page 17

Case Study 10: Voltage Waveform Noise & UPS Switching Page 18 to 19

Appendix: Power Quality Survey Procedures Page 27 to 28

Case Study 11:

Case Study 12:

Voltage Dip in a Factory

Inflow and Outflow of Harmonics

Voltage Drop Caused by Wiring Impedance

Transients Caused by Glow Fluorescent Lighting

Page 20 to 22

Page 23 to 26

- page 1 -

Power Quality Basics

Current Power Supply Environment

Power Quality Standards

Various factors can contribute to worsening power quality

International

Power Quality

Deterioration

Open market

Tough competition to

cut costs

Increase use of PCs

and inverter devices

Connection with new

energy sources (wind,

solar, gas turbine, etc.)

Connection with on-

site power supply

Connection

mixes the

different

power

characteristics

Europe

U.S.A.

Standard Title Published Comment

IEC

61000-4-7

IEC

61000-4-15

IEC

61000-4-30

EN50160

IEEE 1159

IEEE 519

IEEE 446

ANSI C84.1

General guide on harmonics and inter-

harmonics measurements and

instrumentation, for power supply systems

and equipment connected thereto

1991

2002 revised

Actualization of inter-

harmonic concept (from

revision)

Flicker meter - Functional and design

specifications

Testing and measurement techniques

Power Quality measurement methods

1997

2003 A1

2003

120V/60Hz added in

amendment

New standard

Standard Title Published Comment

Voltage Characteristics of electricity

supplied by public distribution systems

1995,

1999 revised

General power quality

standard

IEEE Recommended Practice for

Monitoring Electric Power Quality

IEEE Recommended Practice and

Requirements

IEEE Recommended Practice for

Emergency and Standby Power Systems

for Industrial and Commercial Applications

Electrical Power Systems and Equipment -

Voltage Ratings (60Hz)

1995

1992

1995

Anomaly voltage

Classification of basic

terms

Standards for harmonic

limit values

Describes the CBEMA

curve

Voltage limit values

- page 2 -

ITIC (CBEMA) curve

The ITIC curve judges the allowable level of

voltage RMS fluctuation from the voltage swell,

voltage dip and interruption events.

The analysis is made by the period and depth of

each event according to the limit value of the ITIC

curve.

The ITIC (Information Technology Industry

Council) curve is the most recent version of the

older CBEMA (Computer and Business

Equipment Manufacturers Association) curve.

Both were created by CBEMA. The original

CBEMA curve was widely used in the U.S.A.

Main Power Quality Parameters

1. Transient overvoltage (impulse)

1) Phenomenon

Radical changes in voltage with high voltage

peaks

2) Cause

3) Damage

4) Analysis

Lightning strikes

Power circuit switching

Closure of inductive circuits

Arc to the ground

Load switching

Contact of a bouncing relay

Destruction of power supplies of

equipment

Equipment reset

Waveform (Maximum voltage level, Rise

time, Phase angle, Fluctuation,

Repeatability)

The faster rise time means a closer

occurring point.

2. Voltage Dip

1) Phenomenon

Instantaneous drop of RMS voltage

2) Cause

3) Damage

Large inrush current by turning on heavy

loads

Accident in the distribution network

(Lightning, snow, ice, contact of birds/

trees, effects of accidents)

Short-circuit

Stop or equipment reset

- page 3 -

3. Voltage Swell

1) Phenomenon

Instantaneous rise of RMS voltage

2) Cause

3) Damage

Lightning strikes

Introducing heavy loads

Destruction of power supplies in

equipment

4. Instantaneous Interruptions

1) Phenomenon

Instantaneous or short/long term power

outage

2) Cause

3) Damage

Accident on distribution network

(Lightning, snow, ice, contact of birds/

trees, effects of accidents)

Short-circuit

Stop or equipment reset

5. Unbalance Factor

1) Phenomenon

Imbalance of each phase in 3-phase system

2) Cause

3) Damage

Imbalance of loads by 1-phase load

connection (especially long distribution

lines)

Transformer capacity difference at

receptacle

Overheating of a 3-phase inductive motor

or transformer

Stop equipment by 3E relay tripping (over-

current, missing phase, reverse-phase)

Uneven motor rotation

6. Harmonics

1) Phenomenon

Voltage or current waveform distortion

2) Cause

3) Damage

Thyristor powered conversion devices

Inverter, Variable frequency drives

Overheating, burning, abnormal sounds or

vibration sound caused by the inflow of

harmonic current to the equipment

Malfunctions due to the harmonics voltage

(overheating or burning of reactor for

phase advancing capacitor)

7. Flicker

1) Phenomenon

Regularly repeated voltage impulses spanning

one or more cycles which cause flicker in the

lighting device

2) Cause

3) Damage

Arc/blast furnaces

Arc welding

Flicker in the lighting device

Equipment malfunction

- page 4 -

- page 5 -

CASE STUDY 1

Inrush Current and Current RMS Value of an Industrial Dryer

Environment:

Problem:

Analysis:

Target: 1-phase 2-wire, 100V circuit

This is a simple simulation example.

By using an industrial dryer (100V

AC, 1kW, 50/60Hz), the RMS

fluctuation and inrush current are

measured while switching the dryer

from "OFF=>ON=>COLD=>OFF."

Note:

Model 9694 Clamp on Sensor is

clamped to the 10-turn coil with a CT

setting 0.1.

To record the inrush current event waveform, use the current peak event.

To record the waveform while the dryer is continuously operating in HOT, using themanual event

([ESC]+[EVENT]) is effective.

Current RMS Value Fluctuation

OFF HOT HOTCOLD

The current value while a dryer is working is

10Arms, but the start-up current rises to

10.951Arms.

- page 6 -

Fluctuation of Current Waveform Peak (+) Fluctuation of Current Waveform Peak (-)

Fluctuation of Voltage RMS Value Fluctuation of Active Power RMS Value

A voltage drop of about 4Vrms is measured when the dryer is in operation.

The maximum power is 1.1071kW

Inrush Current Waveform

- page 7 -

CASE STUDY 2

Voltage Drop Caused by Wiring Impedance

Environment:

Problem:

Analysis:

Target: 1-phase 2-wire, 100V circuit

This is an easy simlulation similar to Case Study 1 to monitor the voltage drop caused by wiring

impedance. The voltage at a load shows the voltage drop to the supply side when the wire is thin

and long.

CH2

CH1

When switching an industrial dryer (100V

AC, 1kW, 50/60Hz) from OFF to HOT to

COLD and back to OFF, confirm the

difference in voltage drop between short

and long wirings.

1) When wiring is short

(low wiring impedance without the wires

circled in red)

2) When wiring is long

(high wiring impedance with wires circled in

red)

1) Short Wiring 2) Long Wiring

Voltage RMS Value Fluctuation

Voltage at power supply side

Voltage at consumption side

U1 (CH1: red) is the voltage not affected

by the wiring impedance.

U2 (CH2: green) is the voltage affected

by the wiring impedance.

By adding high wiring impedance, the

voltage drops for 6Vrms on the

consumption side.

The wiring impedance of the wires circled in

red is 0.6-Ohm.

The voltage drop is calculated by using the

Ohm's Law such that "0.6-Ohm x 10A =

6Vrms."

6Vrms

- page 8 -

1) Short Wiring 2) Long Wiring

Current RMS Value Fluctuation

1) Short Wiring 2) Long Wiring

Current Peak Value Fluctuation

In this dryer example, the current consumption at a load is slightly reduced when the wirng is long.

The dryer is a resistive load, so that the current consumption, which means the power consumption,

is reduced by the voltage drop.

If a constant power controlled load is connected, the power consumption is stable despite the

voltage drop. Therefore, the current consumption increases.

When HOT When HOT

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