Client: Gilberti Stinziano Heintz & Smith, P.C.
Pterra was asked to conduct a technical assessment of the impact of a proposed 1,200 MW Marcy-Rock Tavern High Voltage Direct Current (“HVDC”) project (the “Project”) on reliability in the New York State Bulk Power System (“NYSBPS”)1 and on transmission congestion between Marcy and the Lower Hudson Valley, especially the New York State load pockets in New York City and Long Island.
The specific topics of the assessment are: (a) Impact Electric System Reliability and (b) Impact on Transmission Congestion. The specific interfaces in NYSBPS addressed by the analysis are shown in Figure 1.

Figure 1
Table 1 shows the values of interface limits determined by the assessment. The conditions tested differ as to which generating plants are available in the future. All the cases meet performance requirements for thermal and voltage performance based on contingency analysis. The transfer limits show a slightly increasing trend in the upstate interfaces, and a slightly decreasing trend in the downstate interfaces. In all assessments, the Reliability Rules for operation were met.
Table 1: Interface limits in MW for NYSBPS at various conditions.
Condition A |
Condition B |
Condition C |
||||
INTERFACE |
OPEN |
CLOSED |
OPEN |
CLOSED |
OPEN |
CLOSED |
Central East (with Fraser-Gilboa ckt) |
3050 |
N/A |
3050 |
N/A |
3050 |
N/A |
Total East |
N/A |
5775 |
N/A |
5436 |
N/A |
5708 |
UPNY-SENY |
4886 |
5481 |
4939 |
5564 |
5013 |
5731 |
UPNY-CONED |
5316 |
7406 |
4911 |
7022 |
4764 |
6671 |
Millwood South |
N/A |
8393 |
N/A |
9367 |
N/A |
8805 |
Dunwoodie-South |
5025 |
7115 |
5022 |
7134 |
5176 |
7684 |
Historical data on congestion in New York points to frequent congestion on the following interfaces: Central East, UPNY-SENY, UPNY-Coned and Dunwoodie South. With Project in service, the change in average hourly prices over time based on the simulations is shown in Figure 2.
Figure 2: Change in average hourly prices over time

The project reduces the average hourly prices between 2012 and 2015. Prices are highest at the load zones J (New York City) and K (Long Island)
1 The NYS Bulk Power System is “the portion of the bulk power system within the New York Control Area, generally comprising generating units 300 MW and larger and generally comprising transmission facilities 230 kV and above. However, smaller generating units and lower voltage transmission facilities on which faults and disturbances can have a significant adverse impact outside of the local area are also part of the NYS Bulk Power System”.