NamPower engineers and technicians have found a remedy for consistently malfunctioning transformers at the Walvis Bay substation in the Erongo region.
According to a statement, the corporation’s Protection, Telecommunication,
Metering & Control (PTM&C) team designed, tested, and successfully implemented a simple yet reliable Automatic Voltage Regulation (AVR) solution for Walvis Bay substation transformers.
The PTM&C section is responsible for installation, testing, maintenance and fault finding of protection, telecommunication, metering, and control equipment in NamPower substations to safeguard the continuity of supply. The section is also responsible for implementing capital and operational projects.
NamPower explained that three years after its commissioning in 2016, the AVR
device, with which the transformers were equipped, started malfunctioning and failing. These failures were not only observed at the Walvis Bay substation, but also at other substations, namely Okapya and Kuiseb.
“The device in question regulates and contains voltage on the load side within an acceptable margin, while it also ensures equal transformer loading during parallel operation and block tap changer operation under abnormal and system fault conditions to prolong the lives of transformers,” the statement reads.
It continued that during 2020 to 2021, more than five units were replaced due to failure and sent for repairs at the Walvis Bay substation alone. However, even the replaced units began failing after a few months of installation.
“The major problem was the lengthy turnaround time of repair, which takes almost a year, thereby leaving a tremendous burden with power system controllers
and operators to manually monitor and regulate voltages of these transformers in the Walvis Bay substation and other sites,” NamPower explained.
Due to the importance of the Walvis Bay substation, it has a three-fold role in the Erongo region, serving heavy energy consuming industries such as mining, fishing, and tourism. The substation is essential in supplying a wide range of electrical loads in the residential, commercial, and industrial sectors in and around the town of Walvis Bay.
The substation also provides auxiliary power supply to the ANIXAS and Paratus power stations and at the same time dispatching power from these into the network. There are five 40MVA 132/11kV transformers operating in parallel to provide a total power capacity of 200MVA.
“Seeing the importance of the substation and the inconvenience on the system controllers and operators, as well as the huge financial burden on the company, the engineers at PTM&C: Projects and Multidisciplinary started looking into the problem. They discovered a potential solution involving the functional extension of the already-installed SEL 2411 transformer monitoring device to implement voltage monitoring and on-load tap changer control,” said a NamPower spokesperson.
NamPower elaborated that the highly reliable device is quite cost-effective, as the solution costs NamPower about N$4 500 per device. This is as engineers had to procure, install, and programme a three-phase voltage input card into the SEL2411 relays, which previously cost NamPower approximately N$50 000 per device to repair.
“Despite this being the first installation, it took engineers four days to implement and commission this solution on three transformers. This has not only resolved the persistent failure of the initially installed tapcon AVRs but could also serve as a benchmark for future AVR solutions on most of NamPower transformers,” the statement reads.