What is the Styal Loop and why was it used by BR test their new Electric units prior to entering service?

Question

I also understand it was used to test units that had undergone modification as well. I am researching for a book on trains and the Styal loop has cropped up a few times. Thanks.

Answer 1

If you go to Google Earth and look at 53°20'54.51"N 2°14'5.31"W, you will find Styal SSW of Manchester. If you zoom out to 40000 feet and turn on Rail in layers (and turn off road and highways because there are so many of them) you will get the rail lines and see that the section going through Styal is rather straight and isolated from the main line. Back out further to spot Crewe to the south and Manchester to the north.
This pdf http://www.virgintrainsmediaroom.com/media/adobepdf/7/o/British%20Railways%20Era.pdf
on page 13 mentions the loop and its being used back in 1959 for testing, so apparently it has a long history of providing test service. "The Styal Loop of the Crewe–Manchester line was electrified"

Answer 2

The Style loop line runs from Wilmslow station to Slade lane junc north of Stockport via Styal station,it also has a branch to Manchester Airport.

The reason it is often used for test trains is because it can operate independently from the rest of the electrified network by being isolated at each end.

When the 25kv west coast electrification project was being built this was the first section done.
It was also where the 1st AC electric Locos were tested..the 1st one was actually the Metro-vick prototype gas turbine converted to AC to test Loco systems and the overheads.
The loop is close to Longsight maintenance depot which is used for stabling trains on test.