If the range extender is out of range of the main router, you cannot configure it as a range extender anymore.
There are two powerline adapters, right? You may try access point mode.
Main router(LAN)-----PA101~~~~~PA101-------(LAN)WA830RE(access point)

Thanks for that - yes the router feeds a Powerline adaptor and I have a couple of things feeding off that (TV and probably something else).

Are there any instructions for "access point" mode? Could I or should I set up a different named wireless network with the WA830RE?

I am a novice at this so answers on one syllable would be appreciated!

It is quite simple to set it up as an access point.
1. Connect your PC to LAN port of WA830RE. Login its web interface.
http://www.tp-link.com/en/faq-375.html
2. Go to Quick Setup and configure it step by step. Choose Access Point as the operation mode and create Wi-Fi name and password for WA830RE. They can be different from your main router.
3. After finish the configuration, connect all devices as I mentioned. Connect to Wi-Fi name of the extender to see if it works. Ensure powerline adapters have been paired properly.

Thanks - all sorted now. I'm rather annoyed with myself for not asking the question some years ago!

Hello,

I have the same architecture, a router, a TL-WA830RE range extender and three AV500 Powerline Adapter with AC Pass Through.
I want to try the same thing. Connect the TL-WA830RE to a powerline adapter and set TL-WA830RE as an access point.
But despite the setup the new wireless network does not have access to the internet.

Can someone post some details on the configuration? Especially the DHCP Settings?

Thank you