Value chain · CLM-0788
In plain terms
If the ground station has several hundred converter units and their diversity is declared, the harmonics standard lets their high-frequency distortion partly cancel while their low-frequency distortion adds up directly, so the hardest limits to meet are on the low-order harmonics below the fifth and not on the high-frequency switching harmonics that inverter designers usually worry about. Without that declaration the standard requires all their distortion to be added up directly, and the low-order harmonics are no longer singled out.
The claim as recorded
By the knowledge base's arithmetic from G5/5's Table 16 summation exponents, which G5/5 permits only where the equipment's operational and locational diversity is declared and otherwise requires linear addition, for a fleet of 479 identical ground converter units the aggregate harmonic voltage would be 479 times one unit's contribution below the 5th harmonic where the summation exponent is 1.0, 82.1 times at the 5th and 7th where it is 1.4, and 21.9 times at the 11th and above where it is 2.0, so the implied per-unit allowance against the above-230 kV planning levels would be 0.0031 per cent of fundamental at the 3rd harmonic against 0.0685 per cent at the 13th, making the 3rd-harmonic allowance 21.9 times tighter than the 13th and 7.8 times tighter than the 5th; on that declared-diversity condition the binding harmonic constraint for a distributed rectenna converter fleet is the low-order harmonics, not the switching harmonics, but without declared diversity every order aggregates at 479 times and that finding does not follow; and because this calculation generously allocates the entire planning level to the plant the real per-unit allowance is tighter still by whatever G5/5 Stage 3 apportionment applies.
Scope and limits
This is not a G5/5 assessment and must never be presented as one. G5/5 Stage 3 sets a connection's limits by apportioning headroom and requires network impedance and resonance modelling that this calculation contains none of. The per-unit figures are an internal design allocation implied by the standard's aggregation exponents, not limits the standard imposes on a converter unit. The RELATIVE finding, that low-order harmonics bind harder than high-order ones for a large fleet, does not depend on the assumed unit count, but it holds only where diversity is declared so that the Table 16 exponents may be used; under the linear addition G5/5 otherwise requires, every order aggregates alike and the per-unit allowance at each order is its planning level divided by the unit count. The absolute per-unit percentages depend on both assumptions above and should be treated as illustrative. Confidence is MED for that reason.
What it assumes
(a) 479 identical units, which inherits the ASSUMED 4.4 MVA unit rating from CLM-0785, with the sensitivity given; (b) that the fleet is treated as M independent harmonic sources aggregating per Table 16 rather than as a single installation assessed at the connection point, which G5/5 clause 6.3.3 permits only on a declared performance of the equipment's operational and locational diversity, without which linear addition shall be used; linear addition, not the Table 16 treatment, is the more conservative reading, and G5/5's Stage 3 procedure may or may not adopt either for a given connection; (c) that the plant is allocated the whole planning level, which it would not be, so the result is generous to the plant.
Where it comes from
This is the project's own working, shown in full:
Condition, verbatim, SRC-239 clause 6.3.3 (page 36): "This form of aggregation is only valid based on a declared performance of the relevant equipment's operational and locational diversity, without which linear addition shall be employed." Aggregation rule, verbatim, SRC-239 Table 16 "Aggregation (summation) exponents": summation exponent (alpha) 1.0 for harmonic order h<5; 1.4 for 5 <= h <= 10; 2.0 for h > 10. Verbatim explanation from the same page: "The exponent is chosen based on the expected average phase angle between the harmonic sources. An exponent of 1.0 implies that they are in phase (angle 0 degrees), while an exponent of 2.0 implies that they are at an angle of 90 degrees to each other. An exponent of 1.4 implies an angle in the region of 70 degrees." (The source prints the degree symbol; transcribed here as the word.) Arithmetic in full, for M identical sources the aggregate is M^(1/alpha) times one source. M = 479. alpha = 1.0: factor 479.00. alpha = 1.4: 479^(1/1.4) = 479^0.714286 = 82.13. alpha = 2.0: 479^0.5 = 21.89. Per-unit allowance = planning level / factor. h=2: 1.0/479 = 0.00209 per cent. h=3: 1.5/479 = 0.00313 per cent. h=4: 0.8/479 = 0.00167 per cent. h=5 and 7: 2.0/82.13 = 0.02435 per cent. h=11 and 13: 1.5/21.89 = 0.06854 per cent. Ratios: 0.06854/0.00313 = 21.9; 0.02435/0.00313 = 7.8. Sensitivity on the assumed unit rating, h=3 per-unit allowance: M=843, 0.00178 per cent; M=702, 0.00214; M=585, 0.00256; M=479, 0.00313; M=422, 0.00355; M=351, 0.00427; M=264, 0.00568 per cent.
Basis: harmonic voltage aggregation across M identical sources using G5/5 Table 16 summation exponents; per-unit allowance expressed as a percentage of the fundamental
Related records
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Cite this
energyaperture.com/c/clm-0788
CLM-0788, Energy Aperture, as of 2026-09-04.
Connected records
Other published records linked to this one. A list, not a judgement.