Before revision: High-voltage transformers with bushings on top, separated by a fire barrier High-voltage transformer fire barriers, also known as transformer firewalls, transformer ballistic firewalls, or transformer blast walls, are outdoor countermeasures against cascading failures in a national electric grid .
After revision: High-voltage transformers with bushings on top, separated by a fire barrier High-voltage transformer fire barriers, also known as transformer firewalls, transformer ballistic firewalls, or transformer blast walls, are outdoor countermeasures against a fire or exposion involving a single transformer from damaging adjacent transformers .