ERA has a similar concept to the riveted armour on interwar tanks. You get a modular armour type that's fully replaceable but with ERA you can get a much lighter package. You don't really see such ERA types in western powers due to fear of infantry support being injured or killed by the ERA detonating.That’s a respectable amount of protection, similar to the Abrams. I think the use of ERA for extra protection reduces the weight of the tank than if you increased the composite thickness, no?
Although heavy ERA isn't a 100% effective method, having it just reduce pen is enough even if you have a rather weak underlying armour value. Very good if you have such old tanks like the T-72B's that Russia and other Eastern Bloc nations have in storage.
From statistics we've been given Kontakt 5 is supposed to give a kinetic munitions reduction of 30-35% with the newer Relikt [Fig 1;] being above 50%.
Now more modern and sophisticate ERA types such as Nozh [Fig 2;] Are highly unusual, what we've been told is they give a 200-300% reduction on munitions of both Chemical and Kinetic types. With this ERA being sold to Pakistan for their older Ah-Khalid tanks it's not too far out of the realms of possibility that China have gotten some of these modules for their own tanks.
[Fig 1;] Being a simple multi layered design with several layers of explosive sheets and metal designed to defeat tandem charges and redirect the kenetic force of a ballistic munnition. Although due to Relikts large size is been relegated to being side protection.
[Fig 2;] Nozh being a little more unusual consisting of several HEAT like charges designed to decapitate and redirect any munition that detonates the block which is why it has such great performance against both munition types, but being a lot heavier.