Power Grid Monitoring: California (CAISO)

Findings report · scored 2020-01-08 to 2026-04-01 · hourly · all times UTC

Summary

Over 6.2 years of hourly CAISO data the monitor fired 9 alerts. Of 3 target events: 1 predicted (Sep 2020 heat wave, 21 h lead); 1 detected (Sep 2022 record demand, 9.7 h lag); 1 missed (Aug 2020 blackouts). 6 alerts fell outside every target window: 1 inside explanatory windows declared in the run config and 5 unexplained.

At a glance

Scored period6.2 years53,973 hours

Target events3

Predicted1 / 3

Detected1 / 3

Missed1

Alerts fired92 first, 1 repeat

Explained1hindsight label

Unexplained50.8/yr; 1.0/yr with explained

How it is scored

An event is PREDICTED if the first alert falls within 168 hours before onset, DETECTED if it falls within 48 hours after onset, and MISSED otherwise. The same windows apply to every event. The reasoning is in “Too early is the same as wrong”.
Onset is the time the grid operator declared the highest emergency level the event reached, converted to UTC.
Consecutive alerting hours count as one alert. A later alert inside a target window is a repeat, with no credit and no penalty.
An alert outside every target window is “explained” if it starts inside an explanatory window declared in the run config, and “unexplained” otherwise.

Target events

Event	Outcome	Lead / lag	First alert (UTC)	Onset (UTC)	Onset basis and source
August 2020 Rolling Blackouts Stage 3 Emergency, rotating outages on Aug 14 and 15	MISSED	—	—	2020-08-15 01:38 2020-08-14 18:38 local	CAISO declared a Stage 3 Emergency. CAISO, CPUC, CEC, Preliminary Root Cause Analysis: Mid-August 2020 Heat Storm, section 3.3.2
September 2020 Labor Day Heat Wave Stage 2 Emergency, no outages ordered	PREDICTED	21 h lead	2020-09-06 04:00	2020-09-07 00:55 2020-09-06 17:55 local	CAISO declared a statewide Stage 2 Emergency. CAISO, system conditions bulletin (September 2020)
September 2022 Record Demand EEA 3 declared, no load shed ordered by CAISO	DETECTED	9.7 h lag	2022-09-07 10:00	2022-09-07 00:17 2022-09-06 17:17 local	CAISO declared an EEA 3. CAISO, Grid Emergencies History Report (EEA3, 09/06/2022 17:17 to 20:00)

August 2020 Rolling Blackouts MISSED

Scoring window: 2020-08-08 01:38 to 2020-08-17 01:38 UTC (168 h before onset to 48 h after).

No alert started inside the window; the last alert before the window was at 2020-06-28 06:00 and the first alert after it was at 2020-09-06 04:00 UTC.

Missed. The demand and generation models were strongly anomalous from about 25 hours before the Stage 3 declaration, but no residual signal (forecast error, imbalance) agreed, so the two-group rule did not fire. An earlier version caught this event only through an imbalance feature normalized with hour-of-day medians from the whole 2020-26 period, which used future data; with that feature made causal, the event is missed.

September 2020 Labor Day Heat Wave PREDICTED

Scoring window: 2020-08-31 00:55 to 2020-09-09 00:55 UTC (168 h before onset to 48 h after).

First alert at 2020-09-06 04:00 UTC, 21 h lead. Models flagging in that hour: demand vs normal, imbalance, and net generation vs normal.

Repeat alerts inside the window: 2020-09-07 03:00 UTC.

September 2022 Record Demand DETECTED

Scoring window: 2022-08-31 00:17 to 2022-09-09 00:17 UTC (168 h before onset to 48 h after).

First alert at 2022-09-07 10:00 UTC, 9.7 h lag. Models flagging in that hour: forecast error.

Every alert

All 9 alert episodes in the scored period, in order. Nothing is left out.

#	Start (UTC)	End (UTC)	Hours	Class	Matched to	Models flagging at start
1	2020-04-29 05:00	2020-04-29 05:00	1	Explained	Explanatory window: COVID-19 demand shift, Apr to May 2020	imbalance
2	2020-06-28 06:00	2020-06-28 06:00	1	Unexplained		net generation vs normal
3	2020-09-06 04:00	2020-09-06 06:00	3	First alert	September 2020 Labor Day Heat Wave	demand vs normal, imbalance, net generation vs normal
4	2020-09-07 03:00	2020-09-07 05:00	3	Repeat	September 2020 Labor Day Heat Wave	demand vs normal, imbalance, net generation vs normal
5	2021-07-10 02:00	2021-07-10 04:00	3	Unexplained		demand vs normal, imbalance
6	2022-04-09 07:00	2022-04-09 08:00	2	Unexplained		net generation vs normal
7	2022-09-07 10:00	2022-09-07 10:00	1	First alert	September 2022 Record Demand	forecast error
8	2023-07-01 08:00	2023-07-01 08:00	1	Unexplained		demand vs normal
9	2024-07-25 03:00	2024-07-25 03:00	1	Unexplained		net generation vs normal

Configuration of this run

Signals, one HTM model each: forecast error, imbalance, demand vs normal, net generation vs normal, imbalance vs normal.
A model flags an hour when its anomaly likelihood is at or above 0.995. A model's warmth is the share of flagged hours over its last 8 hours.
Signals are grouped (table below). The system alerts when 2 of 2 groups are hot for at least 3 consecutive hours.
Warm-up: the first 168 hours are not scored. Learning stays on for the whole run; no labels are used.

Group	Signals	Hot when
structure	demand vs normal, net generation vs normal	2 of its 2 signals flag in the same hour, or the group's mean warmth is at least 0.45
residual	forecast error, imbalance, imbalance vs normal	1 of its 3 signal flags in the same hour, or the group's mean warmth is at least 0.5

Limits

Three target events is a case study. It shows how the detector behaves on these events; it does not establish a detection rate.
The replay treats each hourly value as available at its timestamp. EIA publishes demand about an hour after the operating hour and net generation the next day, so a live deployment at these lead times would need the operator's own telemetry.
"Explained" is assigned in hindsight from explanatory windows declared in the run config. It never counts as a catch, and the alert rate is given both with and without those alerts.
The alert-rule settings listed above were set per region. Only the HTM model parameters, the encoder shape, the one-week warm-up and the consensus method are shared between regions.
628 hours are absent from the run's timebase because at least one input signal was missing in the source data.