Arc faults have been a hot topic in the electrical industry for more than a decade, with much of the discussion centred on aging oil-based medium voltage switchgear and the increased risk that it poses.
While the risk of an arc fault still exists in modern medium voltage switchgear, both the likelihood that it will occur and the damage it can cause are greatly reduced thanks to arc fault tested designs in compliance with IEC 62271.200 and other measures. However, the arc fault safety rating of type-tested standalone switchgear can be easily negated by incorrect installation, which doesn’t properly consider arc ducting, venting and expansion volume requirements.
“In practice, installation contractors or switchroom builders are not always fully aware of these requirements, and sometimes they don’t fully understand the requirements. In some cases, it may be too technically difficult to achieve IEC compliance,” said Dmitry Lazarchuk, Medium Voltage Product Manager, NHP Electrical Engineering.
“In many cases the complete substation or kiosk solution needs to be arc fault-tested to prove it still maintains arc safety ratings of the switchgear. Therefore, the ideal switchgear would have to fully contain the internal arc fault so that arc venting is no longer required,” Mr Lazarchuk continued.
A short-circuit or another malfunction can create an internal arc and when this occurs in a medium voltage cubicle, it can severely damage the installation and possibly injure the operator.
NHP Medium Voltage Switchgear cubicles are designed and type-tested to mitigate the consequences of internal arcs, and therefore protect both the operator and the installation. Through a strategic pressure release system, the internal arc is restricted to the compartment where it originated and it does not spread towards the operator or to other compartments.
The cubicles are specifically designed to minimise the consequences of an internal arc. Forming a key component of this is the option of a built-in arc quenching system, ‘Arc Killer’, which can extinguish an arc in less than 50 milliseconds. Exclusive to NHP switchgear, Arc Killer is a unique worldwide patented system developed in Europe for the DF2 series of air insulated modular type switchgear. It provides an efficient, simple arc fault protection system, not only for switchgear in substations, but also in the ring network – without the need to send a remote trip signal to upstream CB, unlike typical systems based on arc flash relays. The Arc Killer was a critical function when it came to product selection for a recent large-scale water and wastewater facility project in Australia.
“Arc Killer from NHP protects medium voltage switchgear from internal arc damage and allows fast restoration of switchgear, avoiding long downtime and huge financial loss,” said Mr Lazarchuk. “It also ensures the highest level of operator safety in the unlikely event of an internal arc fault, going beyond requirements of the Australian standards. This made it the most suitable product for a recent water and wastewater application that we were involved in.”
Arc Killer takes arc quenching to a new level, providing improved security that protects valuable switchgear and eliminates blast damage to switchrooms caused by the high pressures of expanding gas and temperature generated by arc faults. Not only are the operator and the environment shielded from harm, but the super-swift arc extinguishing system allows cubicles to be back in operation very quickly in the case of an internal fault. Moreover, the Arc Killers’ fast operation allows full containment of the arc fault within the switchgear enclosure without the need for external ducting or venting. Consequently, the substation design is simplified and the arc fault safety rating of switchgear is always maintained irrespective of where and how it is installed.
In addition to NHP’s market leading range of medium voltage switchgear complete with Arc Killer technology, when combined with NHP’s substation automation solutions, such as the MiCOM Px40 Agile relay, end users can improve network efficiency and ultimate reliability. When it comes to utility applications, NHP is your trusted partner.
