Persistence Needed to Track TV/Radio Interference
By Michael Caruso, Field Planner
New York State Gas & Electric Corp,
When a customer calls in with a loss-of-power
problem the utility sends out a line crew. But when the complaint is about TV interference
or the inability to get a specific radio channel, a specialist must be assigned to the
case. TV or radio interference may be caused by many different things--even at
atmospheric change-but one of the first suspected causes is electric utility equipment. To
correct such problems, New York State Electric & Gas Corp (NYSEG) relies heavily on
ultrasonic technology but creativity, persistence, and experience are also essential.
Recently, NYSEG received a call from a cable company complaining that it had lost VHF
channels 3 and 4. These channels are picked up from Syracuse, NY, and transmitted through
the company's cables.
A visit through the facility determined that there was electrical interference-an arc
occurring somewhere in the area. The engineer drove up and down the roads in all
directions, checking things out, and finally located the problem pole, about a mile away,
in the opposite direction from the cable company's directional antenna.
The general area of the arcing was found with a Model 610 locator, manufactured by Sprague
Micro Tech Manufacturing Inc, Worcester, Mass. This is essentially a radio with a
directional antenna. In this case, it signaled a strong emission, but was not precise
enough to show the exact location of the source from the ground. The engineer then
picked up an ultrasonic instrument known as the Ultra-probe 2000, manufactured by UE
Systems Inc, Elmsford, NY By pointing the instrument and listening for ultrasound from
about 35 feet away, he zeroed in on a horizontal pin insulator. There had been a windstorm
the previous weekend that had broken some of the tie wire just enough slip the 4800-V
primary to the bolt, but not enough to be visible from the ground. A line crew was called
and the problem corrected within an hour. Without the ultrasonic probe, this type of
needle-in-a-haystack situation could take days to solve.
User's equipment often at fault
About half the times that utility troubleshooters visit a facility, it's the customer's
own equipment that's causing the interference-for example, poor wiring, arcing or a
doorbell or furnace transformer. Sometimes, the problem is intermittent and more
challenging to solve. It's important to know what to look for.
At NYSEG, if the problem can't be found from obvious causes
or audible noises at the site, a triangular search is conducted using the Sprague locator.
Different types of arcs produce interference in different radio bands. Complaints
may come from users of cable TV, AM or FM radio, land mobile radio, ham radio operators,
marine radio, etc. The directional capabilities of the Sprague locator are very
dependent on the frequency. Below 88 MHz, it has almost no directional capability,
but it becomes more and more precise as the frequency increases.
When the arc location has been narrowed down as much as possible, troubleshooters start an
ultrasonic search using the Ultraprobe 2000. The instrument has a parabolic dish,
giving it extremely precise directional capabilities. It offers considerable
benefits over older ultrasonic detectors that could only be used with a hotstick from a
bucket truck, which required that a line crew be available.
An ultrasonic detector equipped with a parabolic reflector
can pinpoint problem areas at distances greater than 300 ft. Low-level ultrasonic
signals generated by electrical arcs hit the reflector dish and are concentrated on a
sensitive transducer at the focal point. Background noise from a wide area is
The Ultraprobe is pistol-shaped and battery-powered so that users can easily move about
while searching for arcs. Turning capabilities enable the user to listen to the
signals through headphones to gage their intensity. An analog meter on the probe may
also be used.
Recently, a ham-radio operator called NYSEG about a gross interference problem. In
this case, the feedback was too garbled and faint to use a Sprague locator, so the
engineer walked from pole to pole checking the primary connections with the Ultrasonic
probe. All of these were clean. On the way back, he inspected the neutral and
secondary connections and found a loose 120-V secondary connector going to a streetlight.
The problem was corrected within an hour.
In another case, several customers, including car drivers,
complained about AM radio interference along a particular road. In this case, the
ultrasonic probe showed every pole to be quiet. The Sprague locator had no directional
capability at this frequency, but the engineer did notice a 5-dB increase in emissions as
he walked under one particular pole. A recheck with the Ultraprobe showed the pole
to be quiet, so the engineer concluded it could be a micro-arc inside the poletop
transformer, where it could not emit ultrasound. The transformer was replaced and
the problem disappeared.
The cause of interference in this unusual case was a common bond between the transformer
and TV-cable grounds. This is compulsory in New York State. Result was that the
cable acted as an antenna for the emissions generated inside the transformer and caused
interference on AM radios down 2 miles of road and 200 ft on either side of the line.
When responding to complaints of interference, NYSEG's policy is to check out its
facilities close to the customer's site. But the cause of interference may be 5
miles or more away and be out of the utility's control. Once it has been determined
that no NYSEG equipment is at fault, the customer is advised to call an electrician or