Józef Lorenc

Detection of the intermittent earth faults in compensated MV network

The experience acquired from the Polish medium voltage power distribution networks shows the unreliability of the localization criterions applied to the intermittent earth faults. It results from the lack of stability and low power level of the measuring signals falling often down below the protections start-up level. In the paper, a new adaptive algorithm based on the wavelet analysis enabling detection of specific dynamics of the measuring signal during intermittent earth faults is presented. The algorithm was analyzed utilizing the signals generated in the EMTP program package.

A fuzzy logic- based algorithm for discrimination of damaged line during intermittent earth faults

In the paper, the intermittent earth faults and their detection have been discussed. The intermittent fault belong to the most difficult detectable one due to its low and unstable measuring signals. The discussion has been carried out on the true fault recorded in the typical MV distribution network. It is shown that the criterion values applied, up to now, to the ground-fault protections can be ineffective. Therefore, two versions of an original measuring-decisive algorithm based on fuzzy logic have been proposed. With the algorithm, the faults detection referring to both the knowledge base and the member grade can be carried out.

Efficiency of admitance relays during faults with high fault resistance values in MV networks

In this paper efficiency of the different types of the admittance criteria is described during faults with high value of the fault resistance. The two types of fault are considered: high- ohm resistance in the fault loop and unbalance of the phase load caused by discontinuity of the line feeder with simultaneous occurrence of the ground-fault located behind the gap. Values of the zero sequence signals of current and voltage during those types of faults are shown.

Opportunities of demand flexibility bidding in result of critical peak pricing implementation for low voltage customers in Polish power system

During the summer of 2015 the transmission system operator in Poland was forced to introduce limitations on electricity consumption to important industrial and commercial customers. In absence of sufficient generation reserve in power system this paper undertakes an analysis of the implementation of demand response program based on critical peak pricing for residential customers in a research of the resource that can prevent such shortages and resulting energy price increases. Making use of standard load profiles for customer group under analysis the critical price levels and the price discounts for program participants were designed allowing for the prospective efficient recruitment of program participants. In this way the demand response resource able to offer the important load reduction level comparing to the normal hourly load of participating customer group could be created in a manner financially neutral for the tariff system in force.

Earth fault detection and isolation system for MV network

The detection and isolation of short circuits within the MV networks can be improved by the installation of disconnectors together with short-circuit flow passage indicators (FPI) inside the network. The proposed further improvements of FPI operation based on the change of operating criterion to the admittance one and the installation of zero-sequence resistive current forcing system (AWSCz). The operation of such system is analyzed considering the influence of high transition resistances at the place of fault, errors generated within the zero-sequence current measurement systems as well as the poor setting value divisibility of FPI. The proposed decision making system, placed in HV/MV substation, analyses the information obtained from substation measuring systems and from distributed earth fault FPI sensors to issue the proper decision which sectionalizing disconnectors should be open to isolate the faulted line section.

Time of use tariff design for domestic customers integrating the management goals of efficient energy purchase and delivery

In this paper the effectiveness of demand-side management using zonal tariffs for households is analysed on the case of tariff offer proposed to customers in north-western Poland with the aim to widen the use of electricity for heating purposes. The price elasticity of customers settled according to two zonal tariff was determined using standard load profile of customers published by regional distribution network operator. The costs associated with the applied mean of demand side control were identified and the tariff effects assessment were made taking into account the benefits reached by energy supplier and network operators forming together the considered tariff offer. The analysis presented enabled to formulate some recommendations concerning TOU residential tariff restructuring to improve its feasibility and to create possible prospective income in result of peak load reduction.

Efficiency improving of time of use tariffs for residential customer to create more valuable demand response resource

The means of increasing the impact of time of use tariffs to reduce peak load in the power system caused by household consumers were examined. The introduced concept of TOU tariff elasticity for shifting the demand allowed the comparison of such tariffs offered in Poland by the biggest power sale companies. The estimate of the needed DSR volume to support the safe balancing of the Polish power system was based on the example of the year 2012 for the hours with the highest balancing market prices. To create a share in such DSR resource the implementation of the demand side program with the critical peak rate was proposed for household customers of one of the largest electric energy suppliers in Poland. Basing on the concept of tariff elasticity the possible effects of such a program were presented and the financial risks associated with its implementation were shortly discussed.

Earth fault protection supperted with adaptive admittance criteria

In this paper possibilities for improvement of earth fault protection by adjustment of protective relay settings due to change of neutral point impedance in medium voltage networks are presented. (Zabezpieczenia ziemnozwarciowe wspierane funkcjami adaptacyjnymi). Słowa kluczowe: punkt neutralny, zwarcie doziemne, admitancja, elektroenergetyczna automatyka zabezpieczeniowa

Adaptive functions in G0> and YY0 earth fault protection

In this paper, the benefits resulting from the application of YY0 and G0> earth fault protection with adaptive functions − limiting the risk of outsiders being shocked and reducing the likelihood of two-phase short-circuiting with the ground, are presented. The possibilities of improving the effectiveness of admittance protection by introducing special adaptive functions in control algorithms of station automation and decision algorithms of YY0 and G0> criteria are shown. The rules for using such functions have been described and it has been shown that they have a very significant impact on improvement the effectiveness of protection system. It can be stated that in typical medium voltage networks and solutions of active adaptive functions, good conditions are obtained for the operation of admittance protections even at several times higher resistances in the place of earth fault than when these functions are deactivated or not implemented.

Estimation of electricity value for households participating in demand response programs

Interruptions in power supply, mainly due to the lack of generation adequacy and the discontinuity of distribution network operation, are significant inconvenience for customers connected to the power network. To quantify the duration of expected outages for customers of Polish power system LOLE and SAIDI indices were applied. The demand response program for customers most exposed to interruptions in power supply is proposed as a support in form of additional income source for their decision to build a backup power such as a standby generator or a modern energy storage. Such support influences the value of the undelivered energy for this group of customers that was estimated and compared with other estimations of such value to asses the prospective success in the implementation of the DR scheme considered.