SURGE ARRESTORS

[ELECT 1]

We have have a lot of issues with council transformers and equipment being tampered with, creating power surges in peoples home's. So we install surge arrestors.
The only ones available to us are the CBI ones, in 220v and 380v.
So the instructions are as follows, the line goes into the top, and the earth wire goes into the bottom. This earth goes directly onto the earth terminal in the DB.
Now how does this unit actually work. I assume when more that 230-240v occur, it shorts the live to earth and the main trips.
But how do we know this, So i have been getting g my customer to double their protection, by getting surge arrester plugs on their expensive appliances for that extra protection.
Can any one elaborate or give some other advice on the issue.

[AndyD]

But how do we know this

We know this the same way we know that a circuit breaker will operate if there's a fault, by their certification of quality. Some devices are not easy to test and surge arrestors are one of them. Yes, they conduct to earth as soon as the supply voltage exceeds the clamping voltage they're rated to. They should have an indicator on them to say they're still operational.

[ELECT 1]

We know this the same way we know that a circuit breaker will operate if there's a fault, by their certification of quality. Some devices are not easy to test and surge arrestors are one of them. Yes, they conduct to earth as soon as the supply voltage exceeds the clamping voltage they're rated to. They should have an indicator on them to say they're still operational.

Yes they do have an indicator light.
Thankyou for your explanation

[ians]

From my understanding Surge/ lightning arresters are "NOT" designed to protect a property from over and under voltage caused by tampering with council equipment or neutral bar theft, something which has become a very common problem in SA.

Personally i believe the neutral bar theft which is costing insurance companies and councils millions in claims for a R50 piece of copper is thanks to private companies which have employed un/semi skilled people then, educated just enough to know that the neutral bar will not always kill you while being removed, then let them go once the contract is complete. They now sit with this knowledge and no work. If you go to scrap yards during the day you will notice hundreds of people selling pieces of shiny bright or burnt copper and pieces of copper pipe. The scrap yard will not purchase the brass water meters but will asssist the seller by cutting the the meter off and returning to the seller. It is as stupid sounds.

In Westmead and Durban there are even a burning sites just next to the scrap yards were the insulation is burnt off any wire collected. People drive past all day long and do nothing about it and we wonder why copper theft is costing the country millions if not billions in lost revenue.

[ians]

Common site in Sydney rd Durban, couple hundred kg of copper being cleaned.

[ELECT 1]

But now some insurance companies are insisting that surge protection be fitted to the houses. I hope this thing will work.

[AndyD]

From my understanding Surge/ lightning arresters are "NOT" designed to protect a property from over and under voltage caused by tampering with council equipment or neutral bar theft, something which has become a very common problem in SA......

Surges and prolonged overvoltage are two different issues entirely. Surge protectors won't protect against a floating neutral which happens on a 3-phase network when a neutral is disconnected.

[SilverNodashi]

Would one need to install surge arrestors between an inverter, and DB board, if it's a off gird solar installation, with an option on the inverter to use Eskom or a generator for backup power?

[ELECT 1]

Surges and prolonged over voltage are two different issues entirely. Surge protectors won't protect against a floating neutral which happens on a 3-phase network when a neutral is disconnected.

Andy, you now get a 380v+N surge arrestor and a 220V L+N surge arrestor. This might just alleviate the burnt neutral problem.
I am speaking under correction here though

[AndyD]

Would one need to install surge arrestors between an inverter, and DB board, if it's a off gird solar installation, with an option on the inverter to use Eskom or a generator for backup power?

Specifying surge arrestors is usually via a risk assessment which would determine the likelyhood of surges due to the frequency and density of lightning strikes in that particular area along with the susceptability of the equipment and the equipment cost etc.

If the generator was manufactured as a back-up power generator and it's properly installed then the risk of surge events with the inverter/generator/Solar PV system shouldn't be any higher than the risk of surge with a normal Eskom supply. In Cape Town the frequency of lightning is often in the hundreds of years so surge protection wouldn't be worth the outlay unless you had particularly expensive equipment in your house. JHB is a higher risk area but I've never done an assessment there so I couldn't give you figures. It's also worth noting that surge protectors alone won't guarantee protection against a direct strike on a house, they're only really effective for strikes in the local area.

Andy, you now get a 380v+N surge arrestor and a 220V L+N surge arrestor. This might just alleviate the burnt neutral problem.
I am speaking under correction here though

Yes you do but domestic surge protection can't cope with the duration and the sheer amount of energy that would need to be passed through them in the case of a floating neutral causing the voltage to exceed their clamping voltage. In the world of domestic surge protection a few miliseconds is considered a long surge duration, a floating neutral would cause an overvoltage event that last far longer than this, quite often it could last minutes or even hours.