Australian mining consultant Tony Reczek was giving evidence at the Royal Commission Inquiry into the Pike River mine disaster yesterday.

Reczek, who is an electrical engineer, was employed by the New Zealand Department of Labour to investigate the possibility of electrical sources being a point of ignition for the explosion.

He said having electrical systems underground meant they were in a hazardous environment because it enhanced the possibility they could ignite with methane.

Reczek told the commission the electrical equipment at Pike River was not explosive protective.

“It would appear to me that they were relying on the methane protectors to provide the means of protection if methane were to be present,” he said.

While Reczek had not yet finalised his report with the DOL, his investigations to date revealed a stark relationship between an underground water pump being turned on by Daniel Duggan in the control room and the explosion occurring soon afterwards.

Going into more depth, Reczek explained the mechanics of Pike River’s electrical system, which used variable speed drives to control the start-up and speed of the equipment’s motor.

Reczek said VSD devices used in the mine were evidently causing “harmonic currents” to circulate in the power supplies.

While the harmonic currents were a normal feature resulting from the use of VSDs, Reczek said they needed to be controlled.

“What would be undesirable is for those harmonic currents to find themselves outside of the immediate area where they are created,” he said.

Reczek believed one of the likely causes of ignition was arcing, or big sparking, triggered by harmonic currents coming from the use of VSDs.

His theory was that the switching on of the pump in the control room created an ignition potential because arcing as a result of the harmonics would “basically light the entire electrical system up like a Christmas tree”

“Essentially, the harmonic current flowing in the earth circuits of the underground power supply would be capable of generating incentive sparking across any mechanical surface connected in the connection in the earth circuit,” he said.

Reczek explained that the white flash, seen by survivor Daniel Rockhouse, was likely to have been that of the explosion rather than the arcing which ignited it.

However, it appeared there was a very close “coincidence between the pump starting and the flash appearing”

Reczek said any piece of intrinsically safe equipment should simply not be arcing.

“It’s just not acceptable under any circumstances,” he said.

Reczek’s theory was later challenged by lawyer Richard Raymond and Reczek admitted his findings were incomplete because there were too many unknown factors.

“What we're doing is drawing conclusions or inferences, if you like, based on information which is available that isn't conclusive,” Reczek said.

Pike River former general mine manager Doug White and former technical services general manager Peter van Rooyen remain to give evidence at the third phase of the inquiry.