At a glanceSiemens Power Technologies Interna-tional (Siemens PTI) analyzes protec-tion systems using state-of-the-artmethods to optimize operations andeliminate weak points. With the aid ofsystem calculations based on nationaland international standards, and sys-tem and protection simulations, wedevise protection systems that are:

· selective,

· system compliant, and

· technically and economically suitedfor the customer’s requirements.

The challengeAn electrical power system is intendedto operate in a safe manner at alltimes. However, no matter how well-designed, faults will always occur in apower system. Faults are very specialevents in the life cycle of a public orindustrial system, as they can greatlyaffect or restrict operations. They mayalso lead to severe damages to installa-tions and equipment, or may causepersonal injuries, which could be fatal.Therefore, the arrangement of an ade-quate protection system is an indis-pensable and integral part of powersystem design.

Our solutionOur team is comprised of highly skilledexperts in all aspects of system and

machine protection, from converterdesign and equipment protection tocoordination of low-, medium-, high-and extra-high-voltage protection. Wecan advise and offer a comprehensiveservice for power system protection.

Application examples

From a disturbance to an optimizedsystemWhen faults occur, they must becleared as quickly as possible to obtaina high level of system availability withminimum failure probability. There area number of methods available foranalyzing the causes and the behaviorof the network and the protection sys-tem, including:

· analysis of fault records and faultannunciations from protection re-lays, substation control and protec-tion systems, and SCADA systems

· dynamic system and protectionequipment simulation

· weak point analysis, developmentof countermeasures

· verification of the optimized system

Figure 1: Fault analysis – Zone 1 trip of dis-tance protection on remote end due to wrongearth-fault compensation factor settings

From the primary system to theprotection equipmentThe choice of suitable current andvoltage transformers as connectionlinks between the primary and pro-tection systems depends on thesteady-state and transient phenomenaand the technical requirements of theconnected equipment.

Siemens PTI offers the following ser-vices:

· classification according to nationaland international standards

· dimensioning of instrument trans-formers to suit all common pro-tection equipment

· dimensioning of instrument trans-formers when the specifications ofthe primary system and protectionequipment change.

Figure 2: CTDim dynamic simulation

R/Ohm(secondary)-40 -30 -20 -10 0 10

X/O

hm(s

econ

dary

)

-15,0

-12,5

-10,0

-7,5

-5,0

-2,5

0,0

2,5

5,0

7,5

10,0

12,5

15,0

17,5

20,0

22,5

25,0

27,5

30,0

ProtectioncoordinationProtection schemes and settingsfor transmission grids

siemens.com/power-technologies

Our software program, can study anddimension instrument transformers.For more details specific to softwarefeatures and functionality, please visitsiemens.com/ctdim.

Figure 3: Example of distance zone protectionsettings

From the protection equipment to acoordination system protectionSelective system protection must takeinto account the system structure, thesystem elements, different switchingconditions as well as supplier and cus-tomer requirements.

Siemens PTI offers the following ser-vices:

· design of protection systems

· selection of suitable relays and fus-es

· relay consistent setting calculation

· coordination of all protectionequipment

The analysis is based on a comprehen-sive data collection in close coopera-tion with the customer during whichthe system structure, its elements andoperational conditions are collected.

Figure 4: Short-circuit considerations on over-head line

After data collection, instrument trans-formers are checked and/or newly di-mensioned and selected, enablingproper operation of corresponding re-lays. In parallel, an analysis of the pro-tection system concepts is carried out,considering the customer’s require-ments, habits and state-of-the-arttechnology.

Figure 4: Evaluation of protection system per-formance with SIGUARD PSA

Based on all these aspects, the opti-mum protection scheme is devised,which provides the customer the tech-nically and economically best solution.Selective protection coordination andrelay-consistent setting calculationsare then carried out using software-aided, short-circuit and/or system sta-bility calculations.

Figure 5: SIGRADE grading path and gradingdiagram

L1 L1'

L3 L3'L2 L2'

E

Circuit 1 Circuit 2

L1 L1'

L3 L3'L2 L2'

E

Circuit 1 Circuit 2

Published bySiemens AG 2017

Energy Management DivisionFreyeslebenstrasse 191058 Erlangen, Germany

For more information, please contact:power-technologies.energy@siemens.com

AL=N, ECCN=EAR99Subject to changes and errors. The infor-mation given in this document only con-tains general descriptions and/or perfor-mance features which may not alwaysspecifically reflect those described, orwhich may undergo modification in thecourse of further development of theproducts. The requested performance fea-tures are binding only when they are ex-pressly agreed upon in the concluded con-tract.