Presets

PCC Parameters

PCC Voltage (kV, line-to-line)

Short-Circuit Current at PCC, Isc (A)

Max Demand Load Current, IL (A)

Fundamental Voltage V₁ (V) (optional)

Harmonic Currents Ih (% of IL)

h=2

h=3

h=4

h=5

h=6

h=7

h=8

h=9

h=10

h=11

h=13

h=17

h=19

h=23

h=25

h=35

h=47

h=49

Harmonic Voltages Vh (% of V₁)

h=2

h=3

h=4

h=5

h=6

h=7

h=8

h=9

h=10

h=11

h=13

h=17

h=19

h=23

h=25

h=35

h=47

h=49

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Run the calculator to see THD-V, TDD-I, and per-harmonic compliance.

Per-Harmonic Current Compliance

Order	Ih (% IL)	Limit (% IL)	Group	Margin	Status

Per IEEE 519-2014 §5.1, even harmonics are limited to 25% of the odd harmonic limit in the same group.

Per-Harmonic Voltage Compliance

Order	Vh (% V₁)	Limit (% V₁)	Margin	Status

Methodology ▼

THD-V = √(Σ V_h²) / V₁ × 100 [IEEE 519-2014 Table 1]

TDD-I = √(Σ I_h²) / I_L × 100 [IEEE 519-2014 §10.2]

Isc/I_L ratio selects the current distortion limit row from Table 2 (≤69 kV), Table 3 (69–161 kV), or Table 4 (>161 kV).

Even harmonics are limited to 25% of odd harmonic limits in the same group (§5.1).

Harmonic groups: h<11 · 11≤h<17 · 17≤h<23 · 23≤h<35 · h≥35

Voltage distortion limits (Table 1): LV ≤1 kV → THD 8%, indiv 5%; MV ≤69 kV → THD 5%, indiv 3%; HV 69–161 kV → THD 2.5%, indiv 1.5%; EHV >161 kV → THD 1.5%, indiv 1%.

FAQ ▼

What is IEEE 519-2014?

IEEE 519-2014 is the IEEE Recommended Practice for Harmonic Control in Electric Power Systems. It sets limits on voltage and current harmonic distortion at the Point of Common Coupling (PCC) — the point where a customer and utility connect.

What is TDD vs THD?

THD (Total Harmonic Distortion) expresses harmonic content relative to the fundamental component. TDD (Total Demand Distortion) expresses current harmonics relative to the maximum demand load current IL, not the actual load. IEEE 519 uses TDD for current limits — this prevents a lightly loaded system from appearing compliant when running at, say, 5% load.

How does Isc/IL affect the limits?

Higher Isc/IL ratios mean the utility grid is stronger (stiff source) relative to the load, so it can absorb more harmonic current. IEEE 519 grants higher limits for stiffer grids — a ratio < 20 gets tightest limits; ≥ 1000 gets the loosest.

What is the even-harmonic rule?

Per IEEE 519-2014 §5.1, even-order harmonics (2nd, 4th, 6th…) are subject to limits that are 25% of the corresponding odd harmonic limits. This reflects that well-controlled equipment produces very little even-order distortion in practice.

Which voltage class applies to my project?

Use the line-to-line voltage at the PCC: LV ≤ 1 kV uses Table 1 voltage limits (THD 8%); MV ≤ 69 kV applies Table 2 current limits (THD 5%); HV 69–161 kV applies Table 3 (THD 2.5%); EHV > 161 kV applies Table 4 (THD 1.5%).

What are typical harmonic sources?

Six-pulse VFDs and rectifiers produce 5th, 7th, 11th, 13th harmonics (orders 6k±1). Twelve-pulse drives cancel 5th/7th and start at 11th/13th. UPS and server power supplies produce 3rd, 5th, 7th. Voltage-source inverters (solar/BESS) can produce a wide spectrum including inter-harmonics.

Harmonic Distortion Limits