IEEE Outage Metrics

Question 1

What does sustained interruption mean?

Answer 1

Outage lasting longer than the momentary threshold (usually >5 min). Counts toward SAIFI/SAIDI, not MAIFI.

Question 2

What is a Major Event Day (MED)?

Answer 2

A day when ≥10 % of customers lose power during a catastrophic event. Utilities may exclude MEDs from normal‑day reliability metrics.

Question 3

Relationship: CAIDI vs SAIDI & SAIFI

Answer 3

CAIDI = SAIDI ÷ SAIFI. (Average outage length = total minutes per customer ÷ outages per customer.)

Question 4

SAIFI – short definition

Answer 4

How often the average customer has a sustained outage in a year (interruptions/customer).

Question 5

SAIFI – formula

Answer 5

∑ Customer Interruptions ÷ Total Customers (unit: interruptions/customer)

Question 6

SAIFI – good vs bad

Answer 6

≈1.0 or less = good. ≥2.0 means customers lose power 2+ times per year.

Question 7

SAIFI – XDL data path

Answer 7

Count sustained ‘Power Fail’ events per meter in electric_intervals, divide by meter count.

Question 8

SAIFI – talk‑track

Answer 8

“With AMI events we cut manual counting; SAIFI updates nightly with no spreadsheets.”

Question 9

SAIDI – short definition

Answer 9

Total minutes the average customer is without power in a year.

Question 10

SAIDI – formula

Answer 10

∑ Customer‑outage Minutes ÷ Total Customers (unit: minutes/customer)

Question 11

SAIDI – good vs bad

Answer 11

<100 min = strong reliability; 200‑400 min indicates issues or big storms.

Question 12

SAIDI – XDL data path

Answer 12

Sum (duration × customers) from sustained events; divide by customer count.

Question 13

SAIDI – talk‑track

Answer 13

“SAIDI answers ‘how long’ in simple customer minutes—auto‑recalculated each month.”

Question 14

CAIDI – short definition

Answer 14

Average length of each sustained outage (minutes per interruption).

Question 15

CAIDI – formula

Answer 15

∑ Customer‑outage Minutes ÷ ∑ Customer Interruptions OR SAIDI ÷ SAIFI.

Question 16

CAIDI – typical target

Answer 16

Many utilities aim for <60 min; >120 min signals slow restorations.

Question 17

CAIDI – XDL data path

Answer 17

Calculated automatically once SAIDI & SAIFI are stored: CAIDI = SAIDI/SAIFI.

Question 18

CAIDI – talk‑track

Answer 18

“CAIDI shows how fast crews restore power once it’s out.”

Question 19

MAIFI – short definition

Answer 19

Average number of momentary (blink <5 min) outages per customer.

Question 20

MAIFI – formula

Answer 20

∑ Momentary Customer Interruptions ÷ Total Customers.

Question 21

MAIFI – good vs bad

Answer 21

<1.0 is excellent; >3.0 means frequent blinks customers notice.

Question 22

MAIFI – XDL data path

Answer 22

Same AMI events; filter outages shorter than threshold (<5 min). Count and divide.

Question 23

MAIFI – talk‑track

Answer 23

“Captures the ‘blinks’ that frustrate customers but hide in SAIFI.”

Question 24

CEMI‑n – short definition

Answer 24

Percent of customers with n or more sustained outages (e.g., CEMI‑5).

Question 25

CEMI‑n – formula

Answer 25

Customers with ≥n outages ÷ Total Customers × 100 %.

Question 26

CEMI – why it matters

Answer 26

Highlights worst‑served pockets even when averages look fine; regulators watch it.

Question 27

CEMI – XDL data path

Answer 27

Group outages by meter, filter count ≥n, divide by total meters; user sets n.

Question 28

CEMI – talk‑track

Answer 28

“CEMI zeroes in on the 2 % of customers hit 5+ times so we can fix those circuits.”

Question 29

Difference SAIFI vs MAIFI

Answer 29

SAIFI counts sustained outages (longer than threshold); MAIFI counts brief blinks.

Question 30

When to exclude Major Event Days?

Answer 30

For routine performance reporting—exclude MEDs; include them in separate ‘all‑events’ metrics for full picture.

Question 31

Unit check: SAIFI / SAIDI

Answer 31

SAIFI unit = interruptions per customer; SAIDI unit = minutes (or hours) per customer.