### There are currently 4 loadflow methods [NR, NR+, PQ, PQ+] available. NR stands for the Newton method, PQ for the Fast Decouple method. The + indicating addition features, including the following:

• None-divergence
• Add a swing bus if necessary
• Turn-off all buses in an island if there is no generation source.

Loss allocation algorithm description could be found Here.

### Contingency Analysis

InterPSS currently supports three types of contingency analysis: N-1 Analysis; N-1-1 Analysis and N-2 Analysis.

• N-1 Analysis

Open each branch in the power network and run complete AC loadflow analysis for each contingency.

• N-1-1 Analysis

First open each branch in the power network and run complete AC loadflow analysis for each contingency. Then for each N-1 contingency, open each branch with branch Mva rating violation and run complete AC loadflow analysis for each N-1-1 contingency.

• N-2 Analysis

Open all combination of two branches in the power network and run complete AC loadflow analysis for each N-2 contingency.

The following three reports are generated after the analysis:

• Non-converged Case

Non-converged loadflow case [ tolerance: 0.0010 pu ]

Case Max Error Info

====================================================================================================

[x]Bus120->Bus200(1) dPmax : 0.00967(pu) at Bus : Bus141, dQmax : 0.01829(pu) at Bus : Bus265

[x]Bus1010->Bus1(1) dPmax : 11.86389(pu) at Bus : Bus1010, dQmax : 4.40034(pu) at Bus : Bus1020

The non-converged case report listed all cases with non-converged loadflow against the tolerance. InterPSS use a non-diverge loadflow algorithm, which guarantees that the loadflow will never diverge.

• Voltage Margin

Bus Voltage Limit: [1.10, 0.85]

Bus Id LowVolt LowMargin Description

===============================================================

Bus340 0.8774 2.7% [x]Bus110->Bus280(1)

Bus141 0.7850 -6.5% [x]Bus110->Bus280(1)

Bus140 0.8437 -0.6% [x]Bus110->Bus280(1)

The voltage margin report lists the lowest voltage for the bus for all contingencies and compare it with a Bus Low Voltage Limit. The description tells which contingency caused the lowest voltage. For example, [x]Bus110->Bus280(1) indicates that the open branchBus110->Bus280(1) contingency caused the lowest voltage.

• Branch Mva Margin

Branch Id MvaFlow MvaRating P + jQ Margin Description

==============================================================+=================================

Bus260->Bus263(1) 56.2 65.0 ( 53.4+j 17.4) 14% [x]Bus110->Bus280(1)

Bus151->Bus150(1) 369.0 300.0 ( 362.0+j 71.4) -23% [x]Bus111->Bus110(1)

Bus111->Bus110(1) 378.3 150.0 ( 368.0+j 87.9) -152% [x]Bus151->Bus150(1)

The branch Mva margin report lists the most severe branch Mva rating violation, indicating with a - sign. The description tells which contingency caused the most severe branch rating violation.