Bullet resistant power transformers

05/10/2017

Mitigate risks and protect assets without compromising performance and reliability.

The challenge 

Transformers serve as critical nodes designed to withstand many operational risks, such as severe weather events and network power fluctuations.There remains an additional risk to these assets: human impacts.

One of our U.S. customers decided to address this risk with an innovative concept that does not require further investment to build a concrete wall around the premises. For the customer, versatility and protection were crucial factors. They requested a generator step-up transformer with 970 MVA at 345kV +2x2.5% - 24.8/21.1/17.3kV with a link board to reconnect the low-voltage side. The three-phase unit also allows for voltage regulation on the high-voltage side as it needs to fit five different generating stations and nine different locations, and most importantly, must be protected against high-powered ballistics.

The solution

A one-of-a-kind bullet resistant shielding was designed to safeguard the generator step-up transformer. This product ensures the highest safety and reliability by incorporating bullet-resistant panels that are mounted directly on the transformer tank. It not only protects the tank and radiator cooling system against bullets, it also shields the conservator, turrets, and the bottom of the bushings.

Mounting the system directly on the transformer minimizes the amount of additional space required for the transformer. The panels can also be adapted to reduce acoustic emissions, and their positioning allows for both maintenance and the movement of air for efficient cooling.

In this special case, only three sides are covered with bullet resistant panels, because the low-voltage side of the transformer is built right next to the generator building. To enable access to pumps and fans for maintenance, some of the panels are designed to be removable.

From fundamental research to solutions 

Mounting panels on transformers is not a new invention: this method has been used to reduce transformer noise for many years. However, our engineers know there is always room for improvement, and so they developed additional features that can be incorporated into this equipment.

Over the course of several studies, we found that a 10mm steel sheet can be easily penetrated by a VPAM Class 7 bullet, and even concrete is not an adequate material for preventing transformer units from harm. We finally came up with a material that deflects VPAM Class 13 (.50 BMG M2 AP) bullets, the highest class of rifle projectile.

 

Technical features

The transformer itself is designed as a versatile unit that may be operated in nine different power-generating locations, which the customer defines before the engineering phase.

To save space and construction costs, the panels are mounted directly on the transformer tank wall using steel brackets. The shielding can be easily installed without additional construction investment, such as walls or a larger foundation.

While in this case the customer decided to protect a newly manufactured unit with our bullet resistant panels, it is also possible to retrofit transformers and reactors already in operation.

With a retrofit solution we can also replace porcelain bushings with polymer or composite resin-impregnated types, so even if a bushing’s insulation is penetrated, it is unlikely to lead to ignition of the oil.