| PURE POWER // JUNE 2007 26 Consulting engineers have been specifying DC Hi-Potting to com- mission newly installed power cable systems for the past century. While this cable test is very popular, the question remains whether it is effective in locating cable system defects that may cause future cable system failures? If not, is there an adequate alternative to ensure that the cable system is free of defects and has been prop- erly installed per the requirements of IEEE cable system standards? Here, I will address this topic based on experience obtained over the past ten years. But first, some history. Specifying Cable System Reliability Power cable diagnostics enable consulting engineers to specify and commission cable systems BY BRUCE BROUSSARD, CSE, Vice President of Operations, Imcorp, Storrs, Conn.
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8/8/2019 Specifying Cable System Reliability
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Consulting engineers have been specifying DC Hi-Potting to com-
mission newly installed power cable systems for the past century.
While this cable test is very popular, the question remains whether
it is effective in locating cable system defects that may cause future
cable system failures? If not, is there an adequate alternative to
ensure that the cable system is free of defects and has been prop-
erly installed per the requirements of IEEE cable system standards?
Here, I will address this topic based on experience obtained over
the cable manufacturers was very suc-cessful in causing conductive defects
to fail in the PILC cable. However,
at that time the technology to detect
partial discharge activity in the cable
did not exist. Since the DC Hi-Pot
test equipment was inexpensive and
simple to use, it was quickly adopted
for field use throughout the electrical
industry.
When extruded dielectric cable (i.e.
HMWPE, XLPE, EPR) was introduced
in the 1960s, the cable manufacturers
were aware that the primary failure
mechanism of this type of insulated
cable was partial discharge (over
95%). In order to implement cable
manufacturing quality controls it was
necessary to develop the means to
detect this electrical phenomenon in
their factories. While the factory par-
tial discharge test—known as a corona
test back in the ‘60s—was able to
detect partial discharge in their cable,
it involved expensive equipment and
required a fabricated shielded environ-
ment to conduct the test.
PILC cable
Hi-Pot factory testing
• Simple
• Portable
Failure Mechanism:
Conduction and PD
Extruded cable
(XLPE,EPR and PE)
Factory PD testing
• ICEA specified
• Industry cont.
Hi-Pot
Failure Mechanism:
Partial Discharge
Technology
Advances
• Hi-Pot destructive
• Other options
evolve
• Advance of DSP
opens door for field
PD diagnostics
PD Reliability
Assessment
• Backed by IEC,
IEEE, and ICEA
• Factory Grade
• 10 years of data
support
• Determine location
and severity
determination
1900 1960s 1990s Today
Figure 1. Timeline of cable system testing
The National Electrical Testing Assn. Maintenance Testing Specifications was de-
veloped for use by those responsible for the continued operation of existing electri-
cal systems and equipment to guide them in specifying and performing the necessary
tests to ensure that these systems and apparatus perform satisfactorily, minimizing
downtime and maximizing life expectancy.
The NETA Acceptance Testing Specifications is a document to assist designers,
specifiers, architects, and users of electrical equipment and systems in specifying
required tests on newly-installed power systems and apparatus, before energizing, to
ensure that the installation and equipment comply with specifications and intended
use as well as with regulatory and safety requirements.
NETA’s specifications include topics such as Applicable Codes, Standards, andReferences; Qualifications of the Testing Agency; Division of Responsibility; General
Information concerning Testing Equipment; Short Circuit Analysis and Coordinating
Studies; System Function Tests; and Thermographic Surveys.
A major featured section includes tests to be performed on Switchgear and Switch-