Second Largest US Grid Operator Proposes Reliability Rules For Data Centers

By Ethan Howland of UtilityDive

The Midcontinent Independent System Operator – the second largest US grid operator after PJM Interconnection – on Friday proposed a set of requirements large loads must meet before they can connect to the grid, including ramping and ride-through specifications.

The “interconnection reliability requirements” framework aims to improve MISO’s visibility into large load “characteristics and behavior, support reliable planning and operational decision-making, and establish scalable and technically justified expectations proportional to demonstrated reliability risk,” the grid operator said in its filing with the Federal Energy Regulatory Commission.

The proposal is a part of MISO’s response to FERC’s mid-June “show cause” orders requiring major grid operators to set rules that meet certain criteria for adding data centers and other large loads to the grid. MISO said it plans to make additional proposals by a Nov. 16 deadline.

MISO’s proposal follows similar actions at the Electric Reliability Council of Texas and the PJM Interconnection aimed at setting reliability standards for large loads after several incidents where data centers suddenly tripped offline, raising concerns about grid stability.

On average, electric demand was relatively flat between 2009 and 2024, growing by about 0.5% a year, MISO told FERC. Now, the grid operator expects 1% to 2% annual growth through 2044, with higher growth rates in the near term, according to MISO, which runs the grid and wholesale power markets from Louisiana to Minnesota.

MISO’s proposal defines “large loads” as those larger than 50 MW, and “computational loads” as large loads that include at least 25 MW of demand from information technology equipment, such as servers, storage and networking hardware.

The separate computational load classification will allow MISO to target certain requirements just to data centers, the grid operator said.

“Computational loads may exhibit rapid and coordinated changes in demand, significant power-electronic behavior, and distinct responses to transmission system disturbances,” MISO said.

MISO’s proposed reliability framework sets requirements for its transmission customers that take service on behalf of large loads. It covers four main areas:

• Visibility requirements

To improve MISO’s visibility into large loads on its system, transmission customers must provide MISO with basic information and modeling data on large load facilities, according to the proposal. They must also provide real-time and day-ahead load forecasts for the facilities.

The information is needed “to support planning studies, operational assessments, and accurate representation of large loads behavior and system impacts,” MISO said.

• Phasor Measurement Unit requirements

The PMU requirements set monitoring expectations for computation loads through high-resolution, time-synchronized measurements, according to MISO.

“PMU data provides MISO with greater visibility into facility behavior during system disturbances and rapid operating changes, supporting model validation, performance verification, disturbance analysis, and identification of potential dynamic interactions with the transmission system,” MISO said. 

• Ramp requirements

MISO said its proposed ramp requirements address the rate at which computational loads may increase or decrease electric use during stable-state transitions. 

“Managing rapid changes in demand helps reduce real-time supply-demand imbalances, sudden change in transmission power flows, and associated operational impacts, while supporting more reliable system operation,” MISO said.

• Ride-through requirements

The proposed measures set minimum disturbance performance requirements for computational loads during voltage and frequency disturbances to reduce the risk of unnecessary disconnection or customer-initiated rapid reductions in demands during system events, MISO said. 

MISO’s proposal includes grandfathering provisions to provide certainty to existing and nearly complete commercial arrangements for large loads. MISO asked FERC to let its proposal take effect on Dec. 4.

MISO plans to file additional large load-related proposals, including for additional transmission products and associated study processes, protections against cost shifts and the treatment of generation service to “electrically proximate” large loads, MISO said.