IV DAS Pilot Project

7. Necessary Complementary Measures

7-1 Independent power security

To prevent power interruption caused by using a distribution transformer commonly with general customers, independent power shall be secured at a source side. However present transformer has being used commonly, so this shall be implemented for supplying a stable auxiliary power.

7-2 Durable management for earthing

As pre-mentioned in clause 6-3, earthing pilferage happened frequently. Therefore when it happen re-installation shall be done right away and special countermeasure shall be established for prevention.

7-3 Managing staff expansion

In present Semarang branch office, managing engineer for SCADA and TDAS is only 1person, which will be a big obstacle in the future when he is absent or when multi-faults happen. Therefore we think that PLN shall try to increase the managing ability for TDAS and SCADA with the allocation of additional manager.

7-4 Unified lock using for control box

Presently various lock is using for locking the control box and, key classification and security is unsuccessful. So lots of time need to open the control box or there is a case of not opening at all.

But when recovering the fault control box must be opened quickly, so in order to prepare for confusion and loss of it we recommend to use a unified lock, keep several keys, manage a register and designate a responsible person for through management.

7-5 Promoting Business Communication with Communication Carriers

As it took considerable amount of time to identify the sources of frequent communication failures resulting from maintenance operations of local communication carriers without advance notice during the trial run period, TDAS staffs of PLN must promote official business communication via official correspondences mutually with communication carriers in order to identify sources of communication failure and make advance preparation in reference to prior notice of communication network maintenance operations from local communication carriers.

7-6 Checking & Maintaining Communication Status & Facilities Regularly

PLN must check communication status continuously and periodically, adjust communication sensitivity where necessary, request relevant communication carriers to improve communication quality, investigate on-site communication resources frequently in order to maintain such resources in optimum conditions and repair them with spare parts as necessary. As the actual tests conducted in Korea for 2 – 3 years have revealed that data communication can be supported if communication level is -90dBm or below, communication quality must be managed to maintain adequate communication level.

7-7 Adjusting Switch Setting Following System Change

If the current distribution system is changed or relocated, relevant set values must be reviewed and adjusted to determine line fault with confidence and improve the accuracy of F.I.

7-8 Realigning the Direction of Switch Control Box

As distribution automation system is exposed to severe conditions in the field and installed in parallel with power line, it is true that the system is exposed to several risks.

Notably in case of SYG 9-4 switch, FRTU installed in control box got out of order twice and was replaced in the end. The source of failure is believed to be the influx of surge from lightening or inrush current, damage to electronic parts because of excessive temperature rise or electromagnetic interference (EMI). To analyze possible causes, voltage meter was installed on the low voltage side to measure voltage fluctuation even though for a short period of time (3 days). However, as the peak voltage was just 216.0V without any significant issue or EMI source in the vicinity, it was hard to discover the cause. Therefore, it is our judgment that it is sensible to realign the direction of control box to face the opposite side of direct sunlight in order to prevent failure arising out of excessive temperature rise.

7-9 Considering Transition to Other Communication Platform

Distribution automation system (DAS) is one of the systems which electrical utilities are focusing intensively on around the world to supply high quality energy to customers as the needs rise increasingly. It takes no genius to see that communication network that provides a conduit of control command and signal reception/transmission plays an important role in ensuring successful installation and operation of distribution automation system. A wide variety of communication platforms have been applied to distribution automation system to date, but, there is no unique answer yet as to what communication technology is most adequate to meet the requirements of distribution automation system as a variety of elements such as locale, system characteristics, frequency and communication timing must be considered.

Distribution automation system involves a variety of communication requirements but they can be summarized into the following 4 elements.

1. Reliability
2. Cost Effectiveness
3. Handle present and future data rates
4. Ease of operation and maintenance

In addition, communication platforms used in distribution automation system of today are as listed in [Table 4-8].

[Table 4-8] Distribution Automation System in use around the World

In conclusion, there is no one most cost-effective communication network for distribution automation system yet and electrical utilities continue to optimize their communication network to meet their changing requirements for cost-effectiveness and reliability. As communication network is evolving so fast and multiplying into a variety of alternatives, prompt response to changes in environment is a must.

Therefore, electrical utilities must try to keep optimizing their communication network to the trade-off between cost-effectiveness and reliability. KEPCO now utilizes several communication platforms as below these days and the share of fiber optic cable network believed to be most reliable is rising continuously.

[Table 4-9] shows the shares of communication platforms applied to the distribution automation system of KEPCO.

[Table 4-9] Distribution Automation Communication Platforms of KEPCO

Among various communication network platforms applied to distribution automation system, fiber optic cable is a highly reliable communication platform and gaining advantages in terms of cost-effectiveness increasingly. Researchers have focused on the reliability and functionality improvement of distribution automation system itself to date. However, as distribution automation system stabilizes over time gradually, significant number of researches are targeting communication network as well as it is emerging as one of the key elements dictating the stability and reliability of distribution automation system. Therefore, rather than the GPRS wireless network adopted for the pilot distribution automation project in Semarang, considering transition to fiber optic cable network which requires significant initial investment but ensures high reliability is actively recommended.

7-10 Reinforcement for Distribution Line Patrol and Examination

According to [Table 4-3-1], the number of fault for SYG 5-4, SYG 5-113 and 291/T1-24ZM switches shows 9 times and 20times respectively, also according to [Table 4-3-3], the number of manual F.I occurring in distribution lines, SYG 5 and SYG 6, shows 7times and 24times respectively. It means we can guess that the fault mainly happen in the rear of those switches.

So in order to find out the fault reasons and prevent more fault, reinforcing for distribution line patrol and examination shall be performed by PLN maintenance team.