Experimetal Study on Electrical Short-circuit

Richard Lu

High temperature induced by electrial short-circuit may ignite th

e surrondings and finally cause a fire.

1. Introduction

Purpose of experimental study on electrical short-circuit and

analysis of the remarks:

Investigation of electrical fires

Understanding the mechanism to prevent related

electrical fires

1. Introduction

• Design a test rig to simulate the electrical sh

ort-circuit and reproduce the elestrical failu

re.• Analye the ignite character and remain rem

arks of the electrical short- circuit.• Provide essential data for fire related resear

ch.

1. Introduction

• 2.1 Test rig for simulating electrical short-circuit

motor

belt

contact plate

Contact plate and conta

ct arm driven by the m

otor-belt device move r

elative to one another.

Electrical short-circuit i

s reproduced while the l

ive line fasten to the co

ntact plate contacts.

2. Experiments

contact arm

• 2.2 Experimantal material - wires

a. Copper wires b. Aluminum wires coated with copper

2. Experiments

• 2.2 Experimantal material - power supply

12V lead-acid battery

2. Experiments

3. Schematic of the experiments

Direct current breaker Failure piont

36V DC power supply

• 4.1 Set up the test rig

4. Process of experiments

• 4.2 Fix the wires

4. Process of experiments

• 4.3 Control the test rig to simulate the electrical short-circuit

4. Process of experiments

• 4.4 Collect the remarks of the failure point

4. Process of experiments

• Short-circuit between copper wires shine blinding light and release a large

amount of heat which can melt the copper wire immediately.

5. Results of the experiments

5. Results of the experiments• Short-circuit between aluminum wires coated with copper is more fierce.

• More intense light and heat are generated. A mount of melting bead is spl

ashed and strong white smoke is generated after the short-circuit.

• Melting bead splashed during short-circuit between aluminum wires coated wit

h copper can ignite more distant combustible material, which is more dangerou

s.

5. Results of the experiments

• Frequently-used copper wires and aluminum wires coated with co

pper were chosn for the experiment.

• The melting point of copper and aluminum are following:

Material Melting point/℃ Ignite point/℃

Cu 1084 —

Al 660 —

Insulating material

PVC — 255 ～ 300

Rubber — 130

Silica gel — 350

PTFE 327 —

5. Results of the experiments

• 36V DC power supply was employed since it is safe for the ope

rating personnel. The electrical short-circuit occured under 36V

DC power supply condition can melt the wire material immedite

ly.

• If the 220V AC which is frequently-used in normal building is

used , the electrical short-circuit will release much more heat an

d the surrounding materials will be ignited much more easily.

5. Results of the experiments

• Signs of Short-circuit were found after the experments for both wires.

5. Results of the experiments

a. Copper wires b. Aluminum wires coated with copper

• Signs of Short-circuit are important evidence left in electric fire

scene.

• The remarks in this study were obtained under ambient

temperature.

However, remarks left in pratical fire scene are often obtained

under fire environment.The difference between them need to be

studied.

• The procedure introduced in this study can be used as a

standard preparation method for electrical short-circuit remar

ks.

5. Results of the experiments

A standard preparation method for electrical short-circuit

remarks is presented.

Short-circuit between copper wires may directly ignite the

insulating materials and induce a fire.

Short-circuit between aluminum wires coated with copper may

ignite the insulating materials and more distant combustible ma

terial, which are more likely to induce a fire.

6. Conclusion