Power system: a reliability assessment using FTA

Abstract

The Fault Tree Analysis (FTA) serves as a powerful tool for system risk analysis and reliability assessment. FTA is a top-down approach to failure analysis, starting with a potential undesirable event and then determining Base event (BE). The undesired state of the system is represented by the Top Event (TE). TE and BE are integrated through electronic logic gates (AND gate, OR gate). The fault tree is a tool to identify and assess the combinations of the undesired events in the control of system operation and its environment that can lead to the undesired state of the system. It is recognized worldwide as an important tool for evaluating safety and reliability in system design, development and operation. In this work, an efficient methodology is utilized to find out reliability assessment of critical and/or complex system. The main features and application of this technique for a power system are discussed. Minimal cut sets are developed by means of Boolean equation method. For main substation all CCF are considered at an average temperature of 35 °C. The objective of this work is to develop a method for power system reliability using the FTA approach. The methodology adopted in this investigation is to generate fault trees for each load point of the power system. This fault trees are related to disruption of energy delivery from generators to the specific load points. Quantitative evaluation of the fault trees represents a standpoint for assessment of reliability of power delivery and enables identification of the most important elements in the power system. The power system reliability is assessed and the main contributors to power system reliability are identified, both qualitatively and quantitatively.

Appendix Nomenclature and abbreviations

Symbol	Event
Q GDi ,	The failure probability of power delivery to ith load
R ps ,	Power system reliability
Q ps ,	Power system unreliability
K i ,	Capacity of ith load
K	Total capacity of the system
R ps	Reliability of the power system
	AND gate
	OR gate
	Basic event
	Top & intermediate event
	Transfer gate

DS	Disconnect switch
CB	Circuit breakers
NL,	Number of loads in the system
TE1, TE2, TE3 and TE4	Power failure to load 1, load 2, load 3 and load 4 respectively.
IE1, IE 10, IE18 and	Failure to deliver energy from generators and lines to load 1, load 2, load 3 and load 4 respectively.
IE26	Failure of energy delivery from generators to lines
IE3, IE11, IE19 and IE27	Failure of generators to load 1, load 2, load 3 and load 4 due to substation component failure respectively.
IE4, IE12, IE20 and IE28	Failure of energy delivery from generator 1 (G1) to load1, load 2, load 3 and load 4 respectively.
IE5, IE13, IE21 and IE29	Failure of energy delivery from generator 2 (G2) to load, load 2, load 3 and load 4 respectively.
IE6, IE14, IE22 and IE30	Failure of energy deliver from G1 to load 1, load 2, load 3 and load 4 through Bus 01 respectively.
IE7, IE15, IE23 and IE31	Failure of energy deliver from G1 to load 1, load2, load 3 and load 4 through Bus 02 respectively.
IE8, IE16, IE24 and IE32	Failure of energy deliver from G2 to load1, load2, load 3 and load 4 through Bus 01 respectively.
IE9, IE17, IE25 and IE33	Failure of energy deliver from G2 to load1, load 2, load 3 and load 4 through Bus 02 respectively.
BE1, BE8, BE13 and BE18	DS06, DS08, DS12 and DS14 fails to remain closed respectively.
BE2, BE9, BE14 and BE 19	CB03, CB04, CB06 and CB07 fails to remain closed respectively.
BE3, BE10, BE15 and BE 20	DS07, DS09, DS13 and DS15 fail to close respectively.
BE4, BE11, BE16 and BE 21	CB04, CB08, CB07 and CB05 fail to close respectively.
BE7, BE12, BE17 and BE22	Failure of lines to load 1, load 2, load 3 and load 4 respectively.
BE5	Failure of generator 1
BE6	Failure of generator 2