Line Losses, Voltage Drop and Voltage Unbalance on Parallel Overhead Distribution Lines

Abstract

It has been a general practice by distribution utilities to parallel overhead distribution lines/feeders in a common right of way and the same pole as they terminate from a common substation. This paper studies the impact of modeling parallel overhead distribution lines. The modeling of this kind of circuits in the regulated status of electric distribution business is important as the modeling can impact line losses, voltage drop and voltage unbalance in the lines. A sample case was set-up and is simulated in two cases; parallel lines modeling and taking the parallel lines individually. The study utilized load flow calculations for analyzing line losses, voltage drops and voltage unbalance. The results showed that line losses are not affected by the kind of modeling applied to parallel overhead distribution lines but voltage drop and voltage unbalance yielded different results in the two cases simulated.

See full paper - Parallel Distribution Lines

Philippine Electric Cooperative Analysis : Circuit Kilometer and Number of Customers

The figure on the right is a graphic illustration of Philippine Electric Cooperative Data for their circuit kilometer of their distribution power lines and number of interconnected customers in their electric systems.

From the figure, Electric Cooperative (EC) number 2 has the lowest number of customers while EC #86 has the most number of customers being served. For the circuit kilometer (CKM), EC #91 has the longest distribution lines while EC #33 operates the shortest CKM.

It is interesting to note that EC #91 has the longest CKM and yet serve a number of customers which is less than the number of customers of EC #86. The area franchise of EC #91 maybe very large and rural that it takes to build, operate and maintain such length of distribution lines with such medium number of electric consumers. EC #86 has the highest number of customers and yet operate a not so longer distribution circuits. It can be hypothesized that the area served by EC #86 is very electric power dense. Same evaluation can be derived with EC numbers 2 and 33.

In this case, regulatory considerations for project investing for Philippine electric cooperatives must consider how the service area of an EC is electrically dense or not. If the analysis above does not stand with the density of the franchise, then EC #91 has over built distribution lines while EC #86 can be said to have efficiently invested in electric power distribution lines for a greater number of customers.

Static Voltage Stability Analysis for Electric Subtransmission Systems

The study of voltage stability as indicated in the Philippine Grid Code (PGC) is the center of this paper. Standards and industry practice for voltage stability problem-solving are cited and were referred when provided an example simulation. Voltage stability is a must when looking at a power system if it can handle load growth and at the same time maintaining acceptable voltage levels at all system nodes pre and post-contingency. The static voltage stability simulations utilized practical solutions for voltage instability which are discussed and evaluated using Power-Voltage (PV) and Voltage-MVAR (VQ) curves. This report serves as a tutorial for practicing engineers on the important topic of voltage stability.

See paper by clicking this - Static Voltage Stability Analysis for Electric Subtransmission Systems

Philippine Electric Cooperative Data

It is interesting to study the electric cooperatives’ data publicly posted in websites. The following websites provides these data:

• Energy Regulatory Commission (ERC)
• National Electrification Administration (NEA)

Primarily, the ERC data has the following columns:

1. Distribution line length in circuit-kilometers (ckm) – this item refers to the existing overhead lines owned by each electric cooperative. The data must include single-phase, two-phase and three-phase distribution circuits operated in the cooperative’s franchise area, irregardless of voltage level.

2. Number of customers – the total sum of all electric consumers in each electric cooperative service area. This may be the total of residential plus commercial plus industrial plus barangay electrification. Normally this data is the number of electric meters being maintained by the cooperative.

3. Sales volume – this data is in MWh unit. The total sales of each electric cooperative in year 2006 which was supplied to the total number of customers and which was procured from the transmission operator or other electric power supply entities.

4. Consumption per customer – this data is obtained from dividing data number 3 to data number 4. Though looking at average, this is an indicator of how much energy is utilized by each facility.

5. Structure – is the ratio of the mix of residential sales plus barangay electrification to the total energy sales. This shows on how “rural” is the service area of the electric cooperative. A higher value of structure tells us that that the service area is that the demand comprises much of residential and barangay electrification which is more rural, while a lower structure value gives an indication that the service area has commercial and industrial bulk of energy users.

6. Density - this data is MWh sales divided by the ckm of distribution lines. This reveals how much dense is the service area of the electric cooperative in terms of loading in distribution lines.

7. Distribution Supply Metering (DSM) charge – this data is presented in peso per kwh is reflected in the electric bill.

NEA has many available data but in this article we will focus only on two:

1. Reliability score – ERC has promulgated reliability guidelines for electric distribution companies using standard indices. Reliability is the capability of the electric cooperative to minimize frequency and duration of unforced outage in their service area. In this data, NEA may have summarized the electric cooperative data into one single score.
2. Power Quality (PQ) score – same with reliability, PQ is a performance indicator for electric distribution companies, but in this case ERC has devised their own indices. Also, NEA may have summarized the electric cooperative data into one PQ single score.

In the coming articles, I will try to analyze these data and extract technical and objective evaluation thereof.

SEARCHING FOR THE NEW ERC CHIEF

Reactions from the senators on the likely to be appointed new ERC Chief, see this link - http://www.journal.com.ph/index.php?issue=2008-07-10&sec=4&aid=66133

The senators talked sense!!!

Winning TransCo bidder to get franchise soon

A Philippine congressman giving some false lessons in power systems, see this link:

Winning TransCo bidder to get franchise soon

News Impacting Electricity Rates

Napocor seeks ERC clarification on rate cut

Power subsidy sought from Malampaya proceeds

PSALM opens bidding for Iligan power plant