The failure resulted in both the power outages that hit the region amid a sweltering heat wave, the utility tweeted, and that they were investigating the cause.
The second outage was reported about 4 p.m. and the first happened just five hours before.
The outage was affected customers in the Rossmoyne and surrounding areas. Some businesses in the Montrose neighborhood were in the dark for nearly an hour earlier Wednesday.
Glendale Water & Power also tweeted that four cooling centers in the city were available for those without home air conditioning in the sweltering heat.
Temperatures climbed into the low 90s by late morning and were expected to top out around 100.
A heat advisory remains in effect across much of Southern California, including the Valley and the Inland Empire, through 9 p.m.