EL CIDThe Modern Way to Test

Stator Core Insulation

Why Core Test?

Predictive Maintenance

Service/Repair

Manufacturing/QA

Requirement for Core Testing

Identify Repairable Damage

Reduce Unscheduled Outages

Schedule Necessary Repairs

Improve Efficiency through Reduced Thermal Stresses

Prolong Machine Life

Predictive Maintenance:

Requirement for Core Testing

Service/Repair:

Determine Fault Location

Assess Severity of Fault

Monitor and Verify Repairs

Requirement for Core Testing

Manufacturing/Quality Control:

Quality Assurance/Quality Control

Baseline Results for Machine Owner

Acceptance Testing

Common Causes of Damage

Relaxation of Core Clamping

Failure of Inter-laminar Insulation

Thermal Creeping

Loose Debris

Rotor Rub

Loose Coils, Wedges

Fault Current

Fault Current

Sample Core Damage

Accepted Test Methods

Large Power Supply Required

Safety Concerns with High Current

Expensive Thermal Sensing Equipment

1) High Power Ring Flux Test - the LOOP test

2) Electromagnetic Core Imperfection Detector - ELCID

Low Power Requirements

No Safety Concerns due to High Current

PROBLEMS WITH HIGH POWERED RING FLUX TEST

• AVAILABILITY OF POWER

• RUNNING HIGH CURRENT/HIGH VOLTAGE CABLES AND MECHANICAL

STRESSES

• TIME REQUIRED FOR TEST

• MANPOWER REQUIRED FOR TEST

• SAFETY PRECAUTIONS AND PROCEDURES

• NO ACCESS TO STATOR BORE WHILE THIS TEST IN PROGRESS

• COOLING OR HEATING TIME BETWEEN TEST/REPAIR/ TEST ETC.

• POSSIBILITY OF INCREASED DAMAGE DUE TO TESTS

- NO COOLING ETC. -

• PHYSICALLY SMALL BUT SERIOUS FAULTS NOT ALWAYS DETECTABLE

IF DEEP SEATED OR BENEATH WINDINGS

THE SOLUTION - ELCID•INITIALLY DEVISED BY CEGB - LOW EXCITATION POWER REQUIREMENTS

•FAST - EASILY SET UP

•LOW MAN POWER REQUIREMENTS

•NO SAFETY HAZARDS OR COMPLICATIONS

•INSTANT TEST RESULTS

•STATOR CAN BE REPAIRED SIMULTANEOUSLY WITH FURTHER TESTING - NO NEED TO COOL DOWN OR DISMANTLE TEST GEAR

•POWER LEVEL TOO LOW TO CASE FURTHER DAMAGE

•FAULTS NOT OBSCURED BY WINDINGS

•SPEED ALLOWS FAST TESTS TO BE CARRIED OUT BEFORE AND AFTER OTHER MAINTENANCE WORK (E.G. WEDGING)

•AUTOMATIC PERMANENT RECORDS FOR FAULT H ISTORY MONITORING OR QA PROCEDURES

•EQUIPMENT VERY PORTABLE

Typical Hydrogenerator Excitation System

Typical Turbo generator Excitation System

System Configuration

Positioning the Chattock

Interpretation of Data

Required Excitation Levels

Loop Test

100% +

ELCID

4%(of rated flux density)

System Configuration

Measuring Fault Current with a Chattock Potentiometer

Digital ELCID - Model 601

Method of Scanning

Method of Scanning

Business Justifications

Improved Machine Efficiency

Increased Reliability

Reduced Outages

Reduced Power Consumption during Test

Alternator with Rotating Field

Functional Layout

Digital Processor

Reference Coil Chattock Coil DistanceTransducer

X-Y Chart Recorder

Signal Conditioning

A/D Converter

RS-232 Interface

Distance Encoder

D/A Converter

Portable Computer

Advantages

Low Excitation Power - 4% Fast - Easy to Setup Low Manpower Requirements Significant Reduction in Safety Hazards Instant Interpretation of Test Results Minimal Risk of Further Damage Ability to Re-Test During Maintenance

Cycle Permanent Data Storage Portability

Suggested Usage

Predictive Maintenance:

Manufacturing/Quality Control:

Service/Repair: Beginning of the Maintenance Cycle During Repair Procedures After Completion of Work

Throughout Stacking Process QA for Final Acceptance Acceptance Baseline Test for End-User

Global Scan at available planned intervals

Excitation & Induced Voltages Across Laminations

Flux produced by Excitation

Voltage induced across one pair of laminations

Voltage induced across damaged laminations

Voltage induced along complete core length

Excitation, Fault Volts and Fault Current

Flux produced by Excitation

Voltage induced across damaged laminations

Fault CurrentPhase angle that Fault Current lags Fault Voltage

Excitation, Fault Volts, Fault Current and Quad Fault Current

Flux produced by Excitation

Voltage induced across damaged laminations

Fault Current

Quadrature component of Fault Current

Watts dissipated due to fault

Excitation, Fault Volts and Fault Currents 1 & 2

Flux produced by Excitation

Voltage induced across damaged laminations

Phase Angle for If2

Fault Current 1 Phase Angle for If1

Fault Current 2

Quadrature Fault Current 1

Quadrature Fault Current 2

Sample Fault Indication (Turbo)