| Transmission & distribution
A plug for Pfisterer’s universal XLPE repair solution
Pfisterer says its Universal Repair Kit offers grid operators a “universal solution for repairing damage to cable systems…suitable for all XLPE- insulated cables, regardless of the cross-section, structure or manufacturer.” And it provides a “permanent repair, not a temporary stopgap.” The concept, developed and successfully implemented in close collaboration with Schleswig-Holstein Netz AG (SH Netz), enables grid operators to repair damaged cable systems within a very short time, even in what Pfisterer describes as “historically evolved” networks. For energy suppliers like Schleswig-Holstein Netz AG, fault-free grid operation is of course essential. But damage to conductors caused by, eg, construction work, ageing or water ingress, can never be completely prevented. When it happens, the damaged cable system has to be replaced quickly. Yet preventive inventory holding for networks that have evolved over a long time is extremely cost-intensive, given the large number of installed cable types and cable cross-sections. SH Netz AG is responsible for 2600 km of 110 kV lines. Of this total, around 80 km is 110 kV
Left: The Pfisterer Universal Repair Kit concept for XLPE-insulated cables
XLPE cable, with twelve different cable
types and cross sections ranging from 240 to 2500 mm2
.
Preparing for emergencies can seem a Herculean task. “We wanted to find a universally applicable fault reserve system for 110 kV cables that could cover all cable types in the network with just a few components,” explains Torsten Kröger, head of operation and service for 110 kV overhead lines and cable networks at SH Netz. “And Pfisterer – the cable-independent manufacturer of the CONNEX cable connection system – was able to provide us with a rapidly deployable solution in a very short time. By minimising both downtime and storage needs, it cuts our costs as a grid operator.” It employs the Pfisterer universal pluggable inner cone cable connection system, which allows cables with different conductor shapes, materials
and structures to be connected. Pfisterer has also
developed a universal epoxy resin joint suitable for underground use, for voltages up to 170 kV. An early successful deployment by SH Netz of the Universal Repair Kit was on a wind farm cable joint fault. The conventional joint was cut out and two cable connectors were fitted to the cut cable ends. Using a prepared connecting cable and two epoxy resin joints, the cable section was quickly brought back into service. “The actual installation time of two days under Covid restrictions was a great achievement, since only half of the trained fitters could be on site at any one time,” said Paul Bausch, sales director North Germany at Pfisterer.
Above: Training SH Netz fitters in the use of the Pfisterer Universal Repair Kit for XLPE-insulated cables Why poles need to get hammered
According to its developer Groundline Engineering, Thor Poletest (aka Thor Hammer) delivers “the fastest non-destructive diagnostics and most trusted business intelligence on the serviceability of timber telecommunications and power poles.”
Groundline says it has been adopted in 12 markets around the world, is replacing pole ‘sounding’, ‘sound dig & drill’ and other non- destructive technologies and is “transforming network asset management.” The Thor Hammer looks similar to a conventional hammer but has an in-built digital display and employs cloud-based software. The hammers are designed to help inspectors easily and safely assess wooden polls simply by striking them. This offers a huge potential improvement over current methods, which sometimes involve removing polls altogether and assessing them off site.
The technology is currently being trialled in the UK, where UK Power Networks, SP Energy Networks and Northern Power Grid are working on a joint evaluation project.
Above: Groundline’s Thor Poletest/ Hammer equipment
Each project partner is trialling a number of Thor devices in several locations and “working with the manufacturers to add extra functionality to the tool.”
The readings taken categorise poles into three groups: good; moderately degraded; and ‘end of life’. The poles are then removed and assessed in the workshop to validate the results. Currently, poles are typically assessed manually with a conventional hammer. Maintenance teams strike each pole, listen to the noise, and make an assessment based on the sound that’s produced. The Thor Hammer sends a shock wave up and down the poles, and the reflected wave is received by a geophone. The measured data is uploaded into a cloud-based system, where the condition of the pole is calculated and the results shown on a digital display. This creates a uniform, automated and efficient way of measuring the health of assets. GPS tagging will also provide confirmation of the locations of poles, making future inspection easier.
With tests being conducted on three different networks, it will be possible to compare the data and determine consistency.
www.modernpowersystems.com | May 2021 | 23
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