CABLE TESTING AND CABLE FAULT LOCATING WITH MINIMUM RISK TO GOOD CABLE

ABSTRACT This training program has been designed to thoroughly instruct personnel in state-of-the-art cable fault locating and cable testing methods. The course uses a combination of classroom lectures, demonstrations and hands-on field experiments to teach the trainee cable testing and cable fault locating. The course material has been selected to train the fault locator, cable tester or troubleman to produce results safely, faster and less expensively, with consistently reliable results. Utilities can realize substantial savings in cable replacement and manpower budgets with HDW’s expert cable fault locating and cable testing training and guidelines.

I. INTRODUCTION

The introduction of extruded dielectric cable has imposed new standards and restrictions on cable fault locating and cable testing. Arbitrary burning, reclosing and high voltage DC testing and thumping are frequently used for fault locating and may be doing as much harm as good. The danger of activating dormant faults or generating new faults with improper fault locating methods is ignored.

II. CABLE FAULT LOCATING

Many utilities are experienced in locating short and open circuits on primary and secondary cables. Proper locating of high resistance or intermittent cable faults, which are the majority of faults, is often tedious, unreliable and time consuming. Reclosing, burning and thumping at unnecessarily high voltage and energy levels are frequently used. The danger of activating dormant faults or generating new faults by these improper locating methods is ignored. Management is, for the most part, not aware that improper testing and fault locating is costing their utility hundreds of thousands of dollars in prematurely-failed cable and its replacement.

III. CABLE TESTING

To guarantee a customer’s uninterrupted service with electrical energy, utilities, testing companies and contractors often use various testing procedures and devices without realizing or understanding the potential danger of damaging good cable. The very testing done to assure service reliability may be causing the cable to fail prematurely. Uncertainty about testing of PE and XLPE insulated cables has put many utilities and testing companies into a dilemma. This course discusses the advantages and disadvantages of present testing techniques. An AC very low frequency (VLF) HV Test Set will be presented which permits testing of service-aged power cables with extruded insulation without initiating and preprogramming new faults in the tested cable.

IV. TOPICS

Establishing a standardized cable fault locating procedure, incorporating available technology and properly training fault locating personnel can produce substantial savings in cable replacement and manpower budgets and reduce customer outage time.

Cable fault locating and cable testing topics which will be covered in this course are:

1. What constitutes a fault?

Fault types; Electrical and physical characteristics of a fault; How faults begin: Mechanical damage, installation defects, manufacturing defects, lead sheath corrosion and fatigue; Concentric neutral corrosion, Insulation treeing; Water.

2. Fault Locating With Minimum Risk to Good Cable.

The right tools to do the job right; Most common fault locations: Dig-ins, insulation defects, plastic and steel conduits, splices, taps and terminations.

3. Analyzing the Fault.

Series or shunt fault; High voltage fault; Open or bolted fault; URD or network fault.

4. Cable Tracing and Splice Locating.

Power frequency (60 Hz); Audio frequency; RF

5. Cable Testing.

Insulation resistance and continuity test; Megger and Multi-Meters; DC hipot testing; Proof testing step voltage test, Phasing stick; AC testing: AC test set, close-in, wait and see; VLF testing.

6. Effects of High Voltage DC Testing on Power Cables.

PIL cables; PE and XLPE cables; EPR cables.

7. Time Domain Reflectometry (TDR).

Theory and limitations; Velocity of propogation; Characteristic Impedance; Typical fault reflections; Cables with different propogation velocities; Three stake method.

8. Low Voltage Methods of Fault Locating.

Bridge and voltage division; Tone generator.

9. High Voltage Methods of Fault Locating.

Safety; Single point grounding; Thumping; Burning; Sectionalizing (Reclosing).

10. High Voltage Radar.

Arc Reflection Method (ARM); Surge Pulse Method; Quick look method; Decay method.

11. Pinpointing Equipment.

Acoustic; Electromagnetic; Lightning & Thunder; Earth Gradient; Audio frequency.

12. Concentric Neutral Corrosion Detection

13. Cable Identification.

14. Systematic Approach to Fault Locating.

Duct and direct buried; URD and network; Distribution and transmission; Primary paper and lead cables, 4 to 35 kV; Primary solid dielectric cables, 4 to 35 kV; Secondary Paper and lead cables, 100 to 1000 V; Secondary solid Dielectric cables, 100 to 1000 V; Streetlighting.

15. Integrated Systems for Fault Locating.

Component systems and retrofits; URD fault locating system (City System); Network fault locating system (Compact and Vario Systems).

V. OBJECTIVE

The objective of this course is to train utility personnel, fault locators and testers in state-of-the-art cable fault locating and cable testing while keeping additional damage to the good cable system to a minimum. At the conclusion of this program, the trainees will:

• Be able to locate faults with minimum risk to good cable

• Be familiar with state-of-the-art cable fault locating and cable testing techniques and equipment

• Be able to select the right tool to do the job right

VI. WHO SHOULD ATTEND?

The course has been designed to train troublemen, linemen, technicians, supervisors and engineers in state-of-the-art cable fault locating and cable testing with minimum risk to good cable. The instructors pay attention to the specific needs of all class attendees.